I think it's been discussed a couple of times but don't think there's a direct (as in direct to IP) app, the ones in appworld need a pc or mac client to run. There may also be one the supports text one printing as well from memory
I usually use HP eprint (you get an email address for the printer you can send things to) or Google Cloud Print if thats any help until a solution appears
There are printers that have their own email address and that can work.
Or, from a wifi-shared pb, find the file using windows' explorer, right click and select PRINT. You will have no real control but you can print that way.
We just bought an Epson NX430 "small-in-one" printer for our home wifi network. It has an email print feature. After I little finagling, we now have an email address set up, and can print from all four laptops, and my PB and Torch, and from my son's iPhone (ugh!). The address works from within an app or for sending files as attachments.