What's it do? Well, it has colour swatches for an awful lot of paint ranges: of the popular modelling ones the only one I couldn't find (grr) was, you guessed it, Army Painter. It also has a neat colour mixer app, and the ability to scan a colour to try and match it.
Now, admittedly, you're restricted by the colour quality of the display and how good the source colour samples are, but they've done the best they can by taking them off the makers websites. There's also a scale calculator, just in case.
I've had a play, and while it's not a replacement for the Mark 1 eyeball, it's quite useful as a guide.
Cost? Free, if you don't mind ads. £4.99 for an ad-free version. Sadly, not available for Android yet.
In other news, Tamsin's last giveaway of her 100,000 views prize draw is a box of Warlord Spartans. Which would, I have to admit, go nicely with the other four boxes of Hoplites in unpainted Ancients box number 2 :D.