This page gives a not-so-brief description of all the hardware used so far in the Push Snowboarding App/Project/Hack.
First, it all starts with a Nokia Phone; we've been using the N8 (for all the cool reasons) but any Symbian^3/Qt device should do it out-of-the-box. Maemo/Meego devices will do it too but someone needs to fork the code to use the official, Qt Mobility's, QBluetooth which shouldn't be too hard, everything related should be in either the
PushN8BtDevice or the
The sensors themselves are really simple and are all connected through Bluetooth using the Serial Port Protocol Profile. The hardware setup for that is trivial: a "Bluetooth Serial Modem" connected to an Arduino Pro Mini. These sensors are all polled by the phone: Phone sends "A", Sensor replies with a string containing the measured values.
This sensor is explained in depth at MotionBox.
Arduino just acts as a oversized "bridge/buffer" that captures the signals from the Polar Receiver, stores them and replies them to the phone when polled.