Someone posted here a standalone unit that was touch screen (5" i believe) that had a computer built in, with wifi, bt, ect. I think that would be a little easier since the size of that unit was smaller than a computer itself. I'll see if I can find it.. But it was only like 150$. Best of all you can mount it in a way that you could remove it when you got off the bike to prevent it getting stolen..
What bike do you have by the way?