I wonder if a purpose built version of the zoombak could be fit into handlebars. Different form factor obviously, and both GPS and GSM antennaes would need to run on the outside of handlebar. Underneath bar tape maybe? GPS works perfectly well in a handlebar bag made of heavy PVC, and GSM is even less picky about "line of sight".
It could have battery recharge wire at either end of handlebar,or a direct connection to dynohub. If it would operate on request only (one of the Zoombak modes), power consumption would not be that big. One problem is, in occasional use GPS takes quite some time to get first position fix.
--J