I think you should be able to read your horse through its body language and behaviour and your horse should feel as though it can communicate to you and will be notice. if you pay attention you'll see that your horse is constantly "telling" you how it feels or sending messages through the silent body language it relys on to survive in a herd invironment ,if people are unable to do this I'm not sure they should be involved with such complex and sensitive animals. call me old fashioned but that's just my opinion that people shouldn't need gadgets to know what's going on with their horse.:)
A lady at my barn had one come out and said the communicator told her three places the horse said he was sore. She said it was the same three places her horse chiropractor has been working on but the owner didn't share that with the communicator. The owner is pretty sold on the communicator.