Hi,
I am a Year 4 teacher, and we recently took 90 8-9 year olds to the British Museum. As well as encouraging the children to look at Egyptian artefacts (not just the secret doors in the library) I ended up chatting to one boy about gadgets. He said he would love to bring his mobile to take pictures and videos of the trip. I asked why he hadn't:
"because we're not allowed Miss Sim" (with a suitably patronising expression)

wishful thinking!
So just thought I'd add some evidence that, at a younger age, children would be motivated by using hand held devices. Mobiles still seem grown up to 8 year olds, whereas maybe by key stage 3 or older the novelty could have worn off for some pupils?
The reason we were talking about taking photos was the trip organiser did not want to take digital cameras off site, in case they got damaged (I took my own). Allowing pupils to use their own devices could side step this issue.
Just some thoughts,
Grace