I work as a software developer for a company that develops autostereoscopic displays (For seeing 3D without glasses - like the Nintendo 3DS will do) and stereoscopic software. We are currently developing a line of products for iOS devices to watch videos in 3D and see images and read comics (eventually) in 3D. So at some point this year when it all gets launched hopefully you can pick one up for like $15 for your iPod/iPhone/even iPad (although I don't know that the iPad version will end up being $15).

Edit: I should add that it appears the Nintendo 3DS is using a parallax barrier (but I don't know how true that is - I've heard it could be using a different system too, haven't seen one though). Our technology is using lenticular mainly, so the images will be quite different from both. Lenticular, for example, preserves the brightness of the image much better than parallax barrier.