True. Or u can kill ur tom-tom market with ur own iTunes app.
The thing about tom-tom is it's a gps device. So u get easy adoption for a gps service. Because you get the pre-established intent to use a gps service.
Basically get noticed with the Tom-Tom(more likely because of pre-established intent) and then come up with an app for other devices. Or like I suggest a browser based app( I don't know if this is currently possible, but am sure it will happen soon)