Researchers have been tinkering with contact and implanted eye sensors and electronics for some while, but here's a way around the problem of powering that gear: use the same light entering the eye to power it.
Amazing and terrifying all at once, reality augmenting contact lenses are nearly real. Like, they're almost here. Circuits and antennas and LEDs in a contact lens, generating virtual imagery, Predator style. In your eyeball. Or, this bunny's: