Hardware and software
What's most interesting about KnowRoaming's offering is the SIM "sticker" concept. Your starter kit includes a sticker and an applicator, which you use to literally stick KnowRoaming's device directly on top of the SIM that came with your phone. The sticker is incredibly thin -- it's designed to permanently sit atop your existing card, with enough clearance to fit into your phone. Of course, as with any fresh-off-the-line product, I experienced some hiccups (folded or bunched-up stickers) when trying to squeeze prototype stickers into certain smartphones (more on that below), but once you've successfully installed the device in your phone, you're good to go.
KnowRoaming is designed to minimize hassle when it's time to switch networks. While you're in your home country, the sticker sits dormant. It's more or less invisible to your phone, and all calls and data will be handled exclusively by your original SIM. When you leave the country, though, the device should switch to the new network automatically. You'll receive a text message detailing local rates; your incoming calls will be forwarded to your roaming number (outgoing calls appear with your home number); and after you add "knowroaming" as your APN, you'll be ready to surf at 3G speeds anywhere you go.
Theoretically, KnowRoaming includes (and requires) two companion apps. One is embedded in the SIM sticker (it's a standard SIM toolkit) and will load immediately after you install the sticker in an unlocked phone. The second is available as a free download from iTunes or Google Play. You'll use the smartphone app to set up your account, which entails selecting a local number (located abroad), configuring the forwarding service and adding credit to your account. The other app (the one embedded on the SIM) can be used for troubleshooting, but even if you see it pop up in your app tray, you'll likely never need to open it.
Calculating whether or not KnowRoaming is a good deal depends on your travel plans and regular data usage. If you're expecting to spend several weeks or months in one country, you'll want to buy a local SIM card. Monthly data often costs less through a carrier abroad than you're used to paying in the US. You'll miss out on the convenience of forwarded calls and the ability to country-hop, but for extended trips, plan to purchase a SIM once you arrive at your destination. Likewise, if you're using tons of data (we're talking a gigabyte or more in a week), but you're planning to move from country to country, KeepGo's 500MB plans are a good option.
However, if you're simply doing some casual browsing, checking email, navigating with maps or even uploading a few Instagram photos each day, KnowRoaming is a solid bet. For example, during a three-day trip to Austria that also included side trips to Hungary and Slovakia, I used 195MB of data, costing a total of $29.25. Those 30 bucks got me from country to country using Google Maps, restaurant searches through TripAdvisor, dozens of tweets and emails a day and 10 or so Instagram uploads, including a few videos. Ten bucks a day for liberal use of a smartphone on a short trip abroad isn't a bad deal.
A work in progress
I've been testing KnowRoaming's SIM sticker since November, and while the product and service have improved significantly during that nearly six-month period, there's still work to be done. Compatibility remains the most significant shortcoming at this point -- theoretically, it'll work with any unlocked Android or iPhone, but certain handsets and SIMs present challenges. When inserting multiple versions of the sticker into an LG G2, for example, it bunched up atop the SIM.
The company's been working to slim down the sticker even further, and have been remarkably successful. Still, while I did finally get the most recent version into a G2, with the phone recognizing the KnowRoaming SIM, the passthrough function didn't work, so the AT&T card that came with the phone wasn't accessible until I popped the sticker off. Similarly, with a Motorola Droid Ultra, the sticker was easy to install, but the phone could no longer access its original Verizon SIM. (I'm told this issue is isolated to Verizon SIMs, with only three reported instances to date.)
I was most successful when using KnowRoaming with an AT&T Moto X, which worked flawlessly even with the first-generation sticker. The device performed exactly as advertised, appearing immediately after a restart and even switching to and from the home SIM when I returned to the US. The service, which was spotty last year, has worked very well in 2014. I still experienced periods of downtime, when KnowRoaming would drop its data connection, but restarting the phone always solved the issue, and issues are now few and far between.
The applicator, meanwhile, is still far from perfect, but you'll only need to use this accessory once. The device is confusing at best, and if you end up with a faulty unit, you may need to apply the sticker manually, which has turned out to be my preferred method even when I received a working applicator. As for the occasional hardware mismatches, there's unfortunately not much you can do at this point. KnowRoaming will send out a new sticker or issue a refund if this happens to you, and while the company's been testing a variety of handsets, there's no official compatibility report available just yet.
I've mentioned KeepGo a few times. It's a service I swear by whenever I need a dependable connection anywhere in the world. I've used KeepGo throughout Europe and Asia -- even in notoriously spotty countries like Cambodia and Indonesia -- without running into a single connectivity issue. Expect to pay $10 for 100MB of daily data or $18 for a 500MB plan. Meanwhile, if you're ready to switch carriers in the US, T-Mobile's free data option is certainly appealing. Keep in mind that speeds may be limited, and while I haven't tried the service myself, several colleagues have been pleased.
Finally, if you're traveling to only one country and staying there awhile, buying a local SIM is likely the cheapest option. This can be a hassle, and you won't be able to get online as soon as you arrive (as you can with KnowRoaming and KeepGo), but assuming you do your homework and research rates in advance, the savings can be worth the time you'll spend buying and activating a local SIM. Of course, you can pair this option with KnowRoaming by using that service until you're able to secure another SIM, so in this case, it doesn't hurt to hedge your bets.
With the exception of T-Mobile's Simple Choice plan, global data is still expensive. Spending $30 on a long weekend abroad does beat dropping $50 or more for the same access, however, and if you're in the majority of cellphone users who don't have access to free data across the globe, KnowRoaming is a generally affordable product that's worthy of your consideration. While the initial run of stickers has already shipped out and pre-orders are currently closed, you should be able to hand over your 35 bucks for a starter kit soon. Fill out this form to join the queue.
Update: We tested KnowRoaming's latest sticker with a Verizon Galaxy S5, and the phone recognized the service right away. Additionally, the Verizon SIM passthrough feature worked flawlessly.