How to make LP mobile

I'd love to be able to use LP on the train or anywhere else that doesn't have a power socket to hand.

Specifically:

• What battery pack should I use?
  ...preferably a rechargeable USB one that I can use as a generic charger for other devices when not using it to power LP
• Can an iPad or mobile phone be used as a screen?
  ...to avoid the flimsy ribbon cables of the LCD and touch overlay that I'm currently using