It's a tiny low power consumption multi-sensor bluetooth device that is supported by various apps including a free datalogger program for ipads and iphones - for £20.60 + VAT. Think it's $25 in the USA.
The sensors are accelerometer, magnetometer, gyroscope, barometer, hygrometer, and infra-red thermometer.
The datalogger for ipads and iphones is called SensorTag and available through the app store.
This looks amazing, has anyone tried it yet?
later - forgot to say that this is supported by a lot of tools for writing your own apps etc.
much later - just noticed that this is for ipad 3 onwards and similar vintage iphones etc., earlier ones won't work. If in doubt check the documentation.
Also, it looks like power and transmission speed are low - you're looking at status checks, not a continuous stream of data, and not from really long range. Still interesting though.