Graham
not quite what you are looking for but etherpad is free and works well on laptops/ smartboard
used it today; the adults i was working with at a meeting at our CLC asked questions of my learners at school in real time, about what i said,... quote of the day "whats the best bit about your Head?" answer from a child "my ears... they stop my glasses falling off!"

we didnt have success with synchroneyes either; a real shame as we were really enthused about the positives opportunities it offered, but no wireless we tried would support more than 10 devices at a time
would like to know if you hear a pda WM version that works
carl