Gary -
I learned some more about VM indicator. It *is* operating on an industry standard. Seems that VM systems use either "FSK" or "stutter tone". From what I've read, the phones that support a VMWI that ties to your phone company's voicemail system support both technologies typically.
Anyway - in the end, not an issue for me: as you note, you get two phones for $59 from T-Mobile. You can then purchase additional phones directly from VTech's website for $29 a piece. I just ordered 3 more yesterday (in addition to the original 2 from T-Mobile), should have them before Friday.
I've had the T-Mobile@Home VoIP system up and running since Saturday night, and so far it has been flawless. Sound quality superb, voicemail great - same as voicemail for my T-Mobile cell phones. I also tried walking around the house, creating a lot of distance between the VTech base station and the other mobile, and the sound never varies (I have a pretty big house), from basement to 2nd floor, opposite ends of the house. Next test will be to take a phone outside the house to see how far I can get from the base station. However it seems that the overalll experience is very good: very clean sound, good volume, no static or hiss. I like the sound quality better than my last set, which was a VTech 5.8ghz system.
As soon as I know the other phones are about to arrive, I'll be putting in my call to T-Mobile to port my existing home number over to their service, and dropping Verizon and AT&T....and start saving $60 or $70 a month.