Rob owns a business and he uses a telephone system called Ooma. Leo says that Ooma is great, and he recently did a KnowHow episode about it. Rob's concerned that being forced into a lifetime subscription may leave users high and dry if it goes out of business. However, it's been around for a few years now and the longer it stays in business, the more likely it'll stay around.
Leo personally uses ObiHai, which is $39 and he gets free calls to the US and Canada as long as he has a Google Voice account. It does not have 911, though.