I have had very good luck with UMA phones to bridge spotty service or places with no reception. Blackberries are your best bet. I had some issues, but recent software fixes has mad the technology perfect. I have had no problem going on and off wifi.

The phone has to support UMA. There is no cost to use UMA. However, if you pay $10 extra month all calls on wifi with UMA are free. Calls do have to start and end on wifi.

Remember the phone will need to be preset with wifi. Also the wifi signal has to be strong because phones have weaker wifi cards then laptops. Lastly, if the wifi is heavily used or has poor signal call quality will decrease significantly. Sometimes if I am downloading larges files and doing allot of work where I have my wifi network stressed or running out of bandwidth I have to turn off wifi because the call starts to suffer.

However, when UMA is used it is great. All your calls, emails, text messages go thru. It is literally like extending a tower near you. Best of all if you roam international and use UMA you do not charged roaming rates (as long as you start a call on wifi and remain on it for the entire duration of the call without getting off wifi – u can turn off automatic switchover for UMA and/or cell network).

I was in a really small town last week. No T-Mobile out there, but the hotel had wifi and my blackberry was able to login. I had UMA and made and received several long phone calls and sent a dozen texts and emails. Without UMA I would have had zero coverage (I wasn’t in a roaming area).