I already finished the construction of the wristbands to but everything on its place.
It looks like this now:
The programming of the ArduinoBT and Processing is still a challenge. I use processing to send signals in specific time intervals to the Arduino via bluetooth so that the Arduino knows if i´m sitting in front of the computer and if not. The problem is, that the Arduino sometimes uses a different serialport to connect to the computer, so the processing cant connect to the Arduino and Arduino don´t get signals. The other problem is, when i´m out of the bluetoothrange, processing crashes. I solved this problem with an applescript which restarts the processing program several times.
If someone have a solution for these problems please let me know.
Next steps:
Improve the programs.
Test it on my body.