i am getting a UMPC and i was just wondering if it is safe to plug a transformer/converter or wotever its called to the power socket on the bike to charge on the move
You can get a power invertor from Maplins but it's an inefficient route to go 12v > 240v > UMPC input. The current draw is probably within the limits of the onboard socket on the F800GS, if not you would need to connect directly to the battery (via a fuse).
I have an airline/car charger for an old HP laptop (12v > 20v) that just happens to output the correct amps with the right plug for my current laptop.
Why not see if you can get a car charger for your UMPC?