Who Knows? adds information to the item tooltip letting you know which of your alt toons knows or doesn't know a learnable spell (i.e. recipe). This helps if you come across a recipe that you think one of your alts could use. Now you wont have to logon to that toon or check the armory to see if they already know it.
After loading this addon, you will need to open each Profession screen on each of your toons so WhoKnows can see what you know and start keeping track.
Please submit bugs or feature requests here.
If anyone is willing to provide translations drop me a line and I'll see about setting it up.