Hi, I'm the creator of Piper Wallet, now part of Cryptographi, Inc (http://cryptographi.com).  I'm glad to see other people working in this space!

I just want to point out that Piper Wallet is and has always been open source (GPLv3), and we've encouraged users to build their own units from day 1 in July 2013. 

We provide the source on our github: https://github.com/piperwallet/Piper
And we also provide full SD card images, so if you already have an SD card and an RPi you don't need to buy anything: http://piperwallet.com/sdimages/

I also want to point out that the OP is being a bit disingenuous when he claims that you can build a "PaperBank" for $60, because he's leaving out critical components that are required to even turn the RPi on.

• Raspberry Pi Model B - $35
• USB thermal printer from aliexpress (linked by OP): $37
• High quality SD card that isn't prone to corruption - $12
• 2a USB Power supply (linked by user 'imnotzorg' above) - $6
• Thermal paper for your printer (cheapest I could find on amazon, 10 rolls) - $10

Those items are required just to get the Raspberry Pi running and printing.  Not to mention that all those items come from separate online stores and all have associated shipping costs.  Assume it costs $10 total to ship all the items listed above and you're already at $110. 

I'm excited to see other people working on paper wallets, but it's a bit disappointing that OP didn't do a bit more searching when starting the project.  Piper supports all the features OP is working on (and a lot more!) so it would have been great to put that development effort into something that hasn't already been done.