In reality, I have a hard time imagining that anyone would be able to distinguish anything meaningful from a display on a contact lens. That's like suggesting that you could read a printed word on a contact lens today. You wouldn't be able to focus on something that is directly on your eyeball.

I think in addition to the technical challenge of actually getting something like this working in a contact lens, the issue of physically being able to make use of such a device needs to be addressed.

To those suggesting a pair of glasses be used instead, I think this is a more practical suggestion for both reasons (the biological and technical). If I try really hard I'm barely able to focus on something as close as my glasses.