Bluetooth Low Energy (BLE) is one of the overlooked heroes of iOS. Part of Bluetooth 4.0, it offers a low-power way to wirelessly connect sensors and other short-range devices to applications that can, with Apple's blessing, run in the background. That means, your phone can track and monitor systems without you having to keep an application open full-time and it won't run down your battery.
Still an emerging technology, lots of BLE projects are just ramping up. I recently had a chance to try out a prototype of Phone Halo's Wallet TrackR system. Small enough to fit in your wallet, the Wallet TrackR uses BLE to virtually tether valuables to your iPhone.
It works like this. You slide the TrackR into your wallet or connect it to your keychain. Once paired with your phone, a background process connects to the unit and makes sure that it stays close. Should you move too far away, your phone alerts you -- and shows you the TrackR's last known location on a map. You won't have to worry about getting up from the table at that restaurant and accidentally leaving your wallet behind.
That's not all the TrackR does. Its press-to-find system lets you activate an audio alert, so you can find items that have slid down between cushions. A "cold and hot" indicator tells you how physically close you are to the device.
So how does it work in the real world? Keeping in mind that I only had a chance to test a prototype, pretty well.
The final unit will be quite flat, about 3.8 mm thick. The design is based around two CR2016 batteries, the CR2032's flatter little brother. You can pick these up for a buck or so apiece at the corner grocery or grab a five-pack with free shipping at DealExtreme for about $1.50. It feels like a slightly thicker credit card and is quite light.
The developer says the two batteries should offer up to a three-year battery life (their marketing materials, however, only promise 18 months) due to BLE's low-duty cycle. You should be able to (as he put it, riffing on Ron Popeil), "set it and forget it." The company has tested the power draw off the prototypes to come to this conclusion.
In use, I found the audio alert to be adequate. It's fairly tinny and high-pitched, so it was a bit hard to track down under normal family conditions -- with the TV on and kids yelling, but once they were hushed, I did quite well finding it in all the places my kids had hidden it. I paid them to play hide and seek with the test unit, to see how well the audio signal worked.
We found that it was quite easy to degrade the signal a bit by putting the unit in the pantry behind a closed door, shoving it under couch cushions, and so forth -- but that for a normal home, the alert worked well enough for the device to be found.
I also tested the "abandoned object" functionality, which provides the device leashing. Once I moved far enough away from the dongle, my phone vibrated and sounded, letting me know I had forgotten to take the dongle with me. This worked, as promised, even when I had other apps open -- such as Mobile Safari and Mail.
Aside from a few minor early prototype bugs, I also noticed that the software did drain my iPhone 4S battery slightly faster usual. The developer says this is due to developer tools that will not be in the final release.
The Wallet TrackR represents an evolution in development, dating back to an original 2009 Bluetooth-based design. Because regular Bluetooth has much different power consumption characteristics, the initial system had only a one week battery life. "It was really a big black ugly thing," explained developer Chris Herbert. "We got it to market and had some initial success, but BLE was the tech we were waiting for."
Phone Halo plans to ship units in April 2013. They will cost US$49.95 per device, although you can pre-order now for just $19 each in a sort of non-Kickstarter Kickstarter campaign. Herbert explains that the company will not charge cards until the units are ready to ship.