The device has to support paging. With Push being used rather than the App remaining open all the time (to save battery life), I can't see paging working properly. There would also have to be some way to disable it when not in the office to avoid embarrassing situations where the mobile starts loudly "talking". Doesn't really sound practical, and, if you are in the office and a page through desk sets is made, it is hoped that you are in ear-shot.