In reply to stuart jones:
Finally bought an Olympus camera and put the app on my old Motorola Defy plus phone. So far, in line of site, I can be 8 metres away and my phone and the camera still communicate, it can be slow to update the live view image, but that is my phone. One feature of the app is a self timer, (why?) but this also has a burst mode, from 2 through to 10, this works like this, set up camera and phone, set up app with self timer of 2 seconds and burst of, say 5, it counts to 2, takes 5 shots processes the images, then counts to 2 takes 5 shots, etc, taking 25 pics in total, So I'm hopeful that a belayer could press once on the phone, put the phone down and carry on belaying without there being any issue for the climber. Hopefully this is useful info, and will test it in Spain in a few weeks