i killed three birds with one stone recently and got myself a 02 Xda orbit mobile phone.
it's more of a pda really, but the beauty of it is that it has a built in gps antenna and runs a windows mobile o.s. so it will run memory map AND TomTom, it's all proper touch screen controls etc and work brilliantly, you can stick in a 2gb micro memory card and it also accepts an external gps antenna for added signal strength. flippin fabulous!
oh, and it only cost me £40 on a twelve month contract!!