As I've written in previous posts, mobile phones don't necessarily offer any greater functionality than many individual devices, but they do offer them all in one small gadget that you are likely to have with you.
Good example was the other day when my students were practising spoken presentations. We had been working on various aspects such as signalling language, intonation, pausing etc and they then were going to practise them in front of the class and give each other feedback. I thought it might be helpful for them to be able to see themselves speaking, particularly to analyse their body language/eye contact etc.
So, I quickly propped my phone up against a book and recorded their presentations. Afterwards I connected my phone up to the TV (many phones have this function these days) and we had a productive look at their performance and they were able to spot many things about their performance that they would otherwise have missed. In fact, several of them asked me to send the video files by email for them to look at.
Below you can see an example of one of the presentations (permission granted by student to reproduce here!), the quality isn't great but decent enough to use in class. Again, another good example of how a mobile phone can be uses impromptu in class.