paintRack lets you to scan the barcode on your current collection to add them to the app. I had a big spreadsheet saved to Google Docs for this purpose, but this is much faster, more user-friendly, and includes a better search function. Paint ranges available currently include Citadel, Old Citadel, P3, Reaper, Vallejo, Minitaire, and Warpaints (the Army Builder paints) and others. You can select which ranges to show and which to hide, too, if you don't use all of them.
They've recently done updates to include some smaller paint ranges, including Scale75, Andrea Color, and Secret Weapon. When adding a P3 paint by barcode, it selected the wrong paint, which I reported through the app. I added the paint manually instead. Within a few minutes I got a response from the developers asking for more info so they could correct the error. I love when companies are quick to jump on these kinds of things.
What makes this app really awesome, though, are the additional features: the wish list, paint sets, and color tools. The wish list is simple enough, you track paints that you're looking to buy. Very handy when you're going to the game store. However, each color also has a link to Amazon so you can purchase it on the fly if, say, your FLGS is out of a color you need.
Where it gets great is with the sets and color tools. Sets allows you to save a particular recipe for your miniatures. Very handy for those large army projects and harder to lose than my paint notebook (which I misplace way more often that I'd care to admit). You can name the set say, Grey Hunters, and then create subsets within it for each item on the minis like Armor, Weapons, Faces, Cloaks and save the paints you used for each in their own subset. So you can pull up exactly what paints you used whenever you need it again. Love it.
My personal favorite, though, would be the color tools. You can select any one of the paints in the collection and it will help you select complementary, analogous, a triad, or matches from the available paint ranges. I have a tough time trying to select other paints sometimes so that's very helpful to me. It's also handy for helping you start working with color theory.
You can use the app with some limited functionality for free. You can track some of the paint ranges and scan in pots you have already one at a time. But for $2.99 you can unlock all the features, including every paint line and the Rapid Scan, which allows you to very quickly add lots of paints at once. I had only been playing with it for ten minutes before I knew it was totally worth spending three bucks on it.
It took me about an hour to scan all 350 or so paints I have across the 6-7 ranges I own (I had no idea it was so many). The Rapid Scan worked really well, except for all the paint pots with barcodes that were old and mangled. Even the best barcode scanner can't help you with that. I had about 40 paints with missing or damaged barcodes that I had to enter manually. But even still, it didn't take very long.
The app has been out a little over a year and my only complaint is that I didn't hear about it sooner. It's currently only available for Android, but I'm not going to cry over that. I've spent plenty of time waiting months or years for iOS stuff to finally come out on Android, so now it's their turn to wait.
If you have a large collection of paint or frequently find yourself looking for a good way to track your paint schemes, I highly recommend you check out paintRack.