anything from �200 to �399 depends on what make / money u are willing to spend on, I myself have the TOMTOM Rider which so far I can't fault, it connects via bluetooth to your phone and has a ear piece that goes on your ear that fits nicely under the helmet, that allows you to hear the direction commands, traffic congestion warnings and speed cameras vicinity.

http://www.tomtom.com/products/produ...146&Language=1