Ollie Bray has just completed a series of 5 posts on the use of the iPhone in education.
Plenty of exciting ideas here, and the applications that he mentions are all cheap !
Of course, you first of all need an iPhone and they aren't cheap... You can get them free on certain tariffs, but I don't have £500 a year to spend on my phone.
Of course, they may well come down in price.

Ollie will be doing some seminars at the Scottish Association of Geography Teachers conference in Edinburgh on the 25th of October, as will I. If you're coming along you'll also find me manning the GA stand in between times...