With Nokia Qt SDK driving bluez via dbus, then I open the resulting /dev/rfcomm* with posix api (as QFile did not emit signals when new data arrives) and a socketnotifyer.

I started my experiments for a simple reason, to have a big font display with my heart rate and a disabled screen dimming, to be able to read it during my 1 our cyclette session from 1/2 meters.

Next step is having espeak saying "please come on, you are going too slow"