(UPDATE 8/30/2010: Nike+ check-in public launch as well as build your own!)
Nike+iPod sensors are small, flat wireless motion detectors that chirp a unique serial number (among other data), to tell your iPod how many steps you have taken, and at what pace. Its a great way to stay in shape.
However, they also make great presence detectors. They all transmit on a single channel, unencrypted, for about 60 feet in the 2.4GHz band. List price? $19.99, or $29.99 for shoe sensor and radio. It also looks kinda trendy too.
One really annoying thing about Foursquare or any other venue check-in application, is having to remember to actually check-in when you arrive. Wouldn’t it be a whole lot better if it worked automatically?
My system could eventually plug into something like stumble.to. If you are not familiar with “stumble.to”, it is a way of providing your MAC addresses for your WiFi laptop and phone to check in for you at the venue when you are present. Currently, it is limited to just a few venues now. But instead of having to lug around your laptop, or connect to the local wifi, you could also have your Nike shoes (or sensor in generic shoes) check in for you.
The backend device would need to be located in the venue, but it is internet-independent, low power, and can be located anywhere in the world.
Currently, its on an electronics bread board and rather bulky, and it talks to Foursquare directly…but it (mostly) works.
Here are some screen shots of my first check-in using this system:
UPDATE: Here is the GSM Nike+ device in all of its breadboard glory: