As I have stated else where in this thread, I have no experience with cell phone boosters.  I have been told they work, but that is just hearsay on my part.  Cell phone coverage is the key.  When we started working with this idea.  We were told there would be too much latency in the phones.  (it was not there).  We were told that the phones would be dropping signal all the time (they don't).  We were told that voice would over run data during peak hours (it does not seem to be a problem).

To check signal coverage, the phone company gave us a phone and told us to drive around the area and watch the signal strength.  That is the way we checked signal in our area.  Cell phone signals are a much more "robust signal" than  900 mhz.