KnowRoaming sticker SIMs can now help more people avoid roaming charges

Remember KnowRoaming? That seemingly magical sticker SIM supposed to be attached on top of your usual one, so you can avoid expensive roaming charges? It's finally available for purchase. KnowRoaming works with a GSM Android, iPhone or Windows mobile device and connects you to a local carrier as soon as leave your home country (where it stays dormant) and enter another one. We first heard of it in 2013, when the startup was trying to raise money for production through a KickStarter campaign. It started shipping kits to its backers in February this year while it was still in beta, but after 12 months of testing, it's now ready for a wider release.

You can get one of KnowRoaming's sticker kits for $30 straight from the company's website and buy credits through its accompanying Android, iOS or web app when you're ready to use it. Those credits are used to purchase unlimited data for $7.99 per day, to pay for data as you use it, or to make phone calls over a network to anyone you want. Call rates, on the other hand, vary per country, but you can always check them on the website before you dial.

A few things to keep in mind, though: the unlimited data offer only works in 55 countries (listed on the website). Plus, even though you can use the SIM card to make local calls anywhere you are, you can only call long distance (anywhere you want) if you're currently in the US, Canada, Australia, New Zealand and South Africa. Finally, the company only ships to select countries -- if you don't live in one of 'em, you might have to stalk eBay or find other indirect means of getting one. Planning to get a kit soon? If you're going out of the country within the next two weeks, make sure to try the service out to get $15 credited to your account for free.