I have found the HOLUX http://www.dvr.holux.com/gpsport-260-pro unit to be one of the best 'bicycle' type GPS based units. Waterproof and reliable. I know of over 20 motorcycle riders in my area who use it.I am Poor, I know my place, I use a pushbike one, Hope I don't have to pay as much as Vibrac's Acewell type ?.
The only problem is, If the Police pull you up, You have got to get to the reset button !!, Quick. Cheers Bill.
Baaa