Flir Systems has adapted the thermal imaging tech that it developed for US army helicopters and put it into an iPhone case.
http://www.bbc.co.uk/news/technology-25664454

In case anyone hasn't seen this, FLIR, the masters of Thermal Imaging cameras, have developed an attachment for the iphone (ie. big, but still handheld, case for the iphone with the IR camera on the back) which offers a pretty good FLIR camera, for about $399. Which as far as I know is a lot cheaper than most, at least any that FLIR make themselves.

I mean you're not going to be able to see things at a great distance, maybe 15 metres judging by the BBC video? But whatever, it's cheap enough that it's almost in my price range... If they will actually ship them to the UK. If I remember right there's kind of a ban on exporting fancy FLIR cameras, although I assume that applies mostly to mil-spec versions and not iphone attachments...