Apologies, I didn't mean to insult, but I actually said in my own thread about this, that I got Live Traffic working via WiFi on my head unit. I'm sorry for snapping.
My Head unit also supports 3G, but I'm just too tight to buy a 3G Sim card or contract + you have to buy the dongle too! So I switch on WiFi Tether on my phone, and it auto-connects. Bim bam bosh, Live Traffic.
The FM Transmitter is exactly what it says it is. Some dedicated Sat Navs have an FM Transmitter, so you can listen to the instructions through your head unit. That is why Primo also has music function etc. So you can have music + instructions going through your radio. Some China Nav's have them built-in and theoretically, they should work okay. I wouldn't guarantee it though. However, if we assume that the FM modules all probably use standardized API's, there is no reason that the FM Transmitter function wouldn't work on any tinpot China nav device.
If I was going to go down that route I'd say hit this device :
[Please Register or Login to download file] Big screen, FM Transmitter, WinCE5, Bluetooth
It's practically a tablet at peanut money. The processor is a little bit on the short side, I've seen them with 600Mhz, but you'd be surprised how efficient WinCE is. A 500Mhz Processor can easily make WinCE feel like a lovely smooth operating system. Don't believe me? Perhaps I'll prove it one day