Can anyone assist me?

I need something really small and portable that can trigger samples, loops and full tracks on stage...
A sampler wont do it as they dont have the sampler time for full tracks
Also I want something more portable than a laptop
So I think I am looking at a Smartphone or a PDA - but it is not easy to find out how to do this

Hardware:
- PDA / Smart phone - to plug into PA
- Midi / Wireless to connect it to:
- Small Keyboard / Qwerty, keys or Trigger pad - to have on stage"
- Would also like to be able to trigger with pedal(s)

Questions:
- What is the best PDA / Smart phone to have?
- What is the smallest keyboard that is still easy to use - maybe 12 to 25 triggers needed.
- Smallest easy to use Midi wireless that is reliable + secure
- What software?

Ideally I would like someone who can set it all up for me / hold my hand!
I am based in London x