
UMA/SignalBoost
This has been an ongoing issue for a number of people, since most new properties are built with foil covered insulation in the walls, a lot of new builds (especially flats) have very poor mobile signal. I used to use a blackberry purely because UMA meant I could make voice calls, SMS and data via wifi when I was at home. SignalBoost was an app which basically did the same job, although not nearly as smoothly.
Then Orange stopped offering the app on newer handsets, and BB seemed to drop UMA completely but that coincided with the BT SmartTalk app which lets me use my landline minutes through wifi on my mobile.
Strangely, none of these other services prohibited international calls, in fact I often make "free local calls" to the UK from other countries (although you do have to remember the free evening period is UK time not local, oops!) so I can't help thinking this restriction is a money-spinner.
It would be great if manufacturers/networks could get us back to a point where all services on a mobile worked via wifi again, including SMS. It used to work, why have we gone backwards?