iPad mini
I've been using the iPad mini for about a year, with run way HD, heli pack pro in the UK.
I keep the iPad in a survivor case, having dropped it a few times I'm glad I done this.
Advantage of having this on a cell network is you can get the weather / notams out in a field as along as you have a signal that is.
The only downside is battery life you'll only get about 2 hours of flying on a fully charged battery, so you need some sort of power supply.