I got the BT adapter when I upgraded my phone to an N95. There's an application for S60 called ExtGPS that turns it into a bluetooth GPS. I've been trying on occasion to get it to work, even if I don't get waypoint support. For some reason though, the N95 and the adapter don't want to automatically connect. I usually end up putting it away for a few months, then think about it and get myself frustrated again. I never thought about trying to use Maemo Mapper on the N800. I'll have to dig out the adapter this weekend and see what happens.