Hi there
I'm currently using TomTom3 complete with their BT GPS unit in my car - its setup using Seidio's universal car mount whch powers my Ipaq 5550 via USB and also powers the TomTom BT GPS unit via a 5v output port.
I would supply a link but Seidio's website is down at the moment, but it you want some photos of the GPS mount (complete with Ipaq & TomTom) then please ask and I'll see what I can do.
[edit]Just had a quick look at the Arkon mount - its the same as my Seidio! So yes, the 5v output can power the TomTom GPS unit, as long as you're got the right lead....
