If the remote devices are the master, how do you regulate when the remote devices decide to communicate? What happens if they all decide to communicate at once? I'm sure your server might die from overload! Think about the concepts GSM uses (as do most mobile phone systems) - it has a number of cell sites that service a number of mobile phones. The cell site is the master and polls the phones in its area. The phones in its area register themselves.

As Andy says, you need someone who has experience with this sort of problem and can understand the possible problems you might have and be able to quantify the outcome. I think your problem is similar to one of a webserver - you can have a number of random connections. The way you manage those connections will be the key to your success. There has been much research done on these kinds of problems. I would suggest you do a search and read - that way you can arm yourself with hard evidence.

If your programmer has no knowlege of finite state machines, how is he going to cope with concurrent connections, multiple threads, interprocess communication, atomicity issues, thrashing and so on. I'm not trying to scare you, but what is ignored now is fairly certain to bite you later on.

For instance - in the early days of web servers, the usual method was to have one thread per connection. This worked fine until you got a large number of connections - handling all those threads created a huge overhead. Now each thread manages a small pool of connections. There's a term for this which escapes me at the moment - socket multiplexing or such like.