I do see that the Mt. Gox Mobile app will scan redeemable codes. It might generate them as well.
Also, you can use any QR code creation tool. The problem with using an online tool to create a QR code is that you never want to expose the generated redeemable code to any service you don't trust.
I might trust, let's say, Wolfram Alpha's, service to create the code securely (without redeeming it themselves). For example:
But this I would only do for a code that is for small amounts and one that will get cashed in within a day or two.
But long-term, use of methods that are not secure will cause bitcoins to be lost. It takes a second for an admin at Wolfram Alpha, for example, to write a regex filter to be alerted any time a search like that is for a redeemable code / bitcoin voucher. But for the moment that method is probably secure because only a few people use it for printing redeemable codes.
Can anyone else who uses Mt. Gox Mobile confirm whether or not it will create the QR code for a Redeemable Code voucher (for BTCs)?