I have a Sony Ericsson MBW-150 and a Fossil/Abacus AU6001 and both behave in practically the same way.

I've been looking at two possibilities..

First is trying to get hold of the source code for pnatd.. This is the daemon that allows the N900 to work like a Hayes/GSM modem (answering AT commands) Adding the Sony Ericsson extensions required for these watches should be trivial..

The alternative (since I don't believe Nokia are going to open this daemon.. booooo!!!) is a tiny switching application..

basically at the moment rfcomm works like inetd, it listens for bluetooth connections.. it then calls pnatd which provides the AT command channel..

I propose a small app that prior to calling pnatd, looks up the remote end bluetooth address (either a watch or maybe a laptop) an calls different commands accordingly.. If a watch is connecting, btwatchd is called instead of pnatd.. This would require storing valid bluetooth addresses somewhere (probably inside gconf) and having a GUI app to define a bluetooth device as a watch..

Either way, I've made some progress porting my AT daemon to include dbus information.. it will report an incoming call but so far nothing on the message front..

There is two levels of support I forsee for such watches..
If the commands the watches expect are implemented according to the publish specs, the watch would behave exactly as expected..

however.. if the daemon (to be written) anticipated the watch it could manipulate the commands beyond their intended spec to create extra functionality.. for example, pretending the phone is ringing in order to alert the wearer of an IM message, or an alarm/calendar event

This would be a non-standard implementation..

I'll try and set up a wiki page on this if there is enough interest.. and I'll try and get a working daemon and upstart script sorted by the weekend.. No GUI (I can't make pretty things) so it'll require some command lines to manipulate gconf..

either way, I hope to have really basic support for the sony ericsson and Fosil watches soon..

hack-tastic!