I used smsZap for a couple of years, but became disenchanted with it. Customer service is woeful with no response received to the emails I've sent them when their service appeared to be down.

The price per message hasn't dropped despite most carriers now providing much cheaper text rates than they did a couple of years. I currently also have a few credits left (enough for a couple of messages) which the software refuses to let me use.

It feels like this app has been abandoned by its developers. They are happy to take my money but don't seem to care whether I continue to use their service or not.