[davidr]

Scala Rider and Interphone are two that are readily available. Both cost about 170 Euros and offer fuss-free wireless connectivity to either your phone or your GPS (or if you're a Zumo owner, you phone and your GPS together through your Zumo)

The main differences are that the Scala has two speakers that go in your helmet and a built in FM radio. The Interphone has only speaker and no radio but has the great advantage of doubling as a wireless bike to bike intercom for a range up to 500 metres (presuming your riding buddy also has the same unit)

Both fit readily onto most helmets via a clamp which fastens onto the inside of the shell.

Scala Marketing is slightly better as if you buy what's known as a 'TeamSet' you get 2 scalas in one box (albeit without an FM radio) for about 250 Euros. For this you can talk wirelessly up to about 10 metres (so well suited to a rider and passenger) or use your phone/GPS

I have a Scala-FM (i.e the one with the radio fitted) and it fits pretty readily to my Arai RX7