Just a quick note if anyone has an android phone/tablet (no older than approx 2yrs) you can now download an app from the play store that runs Boinc (of sorts). It's called HTC Power To Give and before you ask, no it's not just limited to HTC's. I have given it a try and it's starting to add to my credits.
It works only when your phone/tablet is on charge (50% or more battery minimum availability, changeable via preferences) and connected to wifi, and as such it doesn't use any mobile data and runs when not in use.
I've had it running for the past 72 hours on my Samsung Galaxy S3 and it's now showing up in "my computers" and is adding a few credits. I charge my phone in the evenings so it's running from approx midnight to 7am solid.
As mobile chips are nowhere near as powerful as laptops etc don't expect huge credits.
If nothing else look at is as Tesco...every little helps.