I think I used a garmin around the states (was borrowed off a friend as it had US maps) and it worked alright (had 3 minor stuff ups from memory). I use a tomtom and home and it works fine just that you have to put in suburb first which had caused me to use the internet or street directories to find out what suburbs a street is in.
You're only given a little spark of madness. You mustn't lose it.
I have the garmin fitness belt with an app for my cellphone. Marcus has the watch and belt. They are great tools for biking and running. I don't know if I would trust their maps for gps though.