My pal Giovanni send me a link to this video on seeing with the tongue. The idea is simple - use an array of electrodes tied to a grayscale camera to perform position reflecting stimulation of the tongue with intensities that vary with the pixel darkness. For instance, if the top left pixel is black, stimulate the front left electrode minimally. If the pixel tot he right of that is 50% gray, stimulate the next lead on the electrode with 50% intensity. The big issue right now is resolution of the device, but I would think that there is a limitation in general on the resolution a person can discern. I don't know much about density of receptors on the tongue, but I think the number is around 50-100/cm^2. Say the pad can be about 4cm wide when tensed and 5 1/3cm (to maintain 4:3 aspect ratio), that's between 1066.6 and 2133.3 pixels total. To put that in perspective, those junky 14" monitors from over a decade ago, what went up to VGA resolution (640x480) 307,200 pixels. That that's not even taking into account any local crosstalk, which could work for or, more likely, against better resolution. Maybe some sort of fovea limitation, with a dispersion from the center, though a the fovea, the human eye's resolution is about 500 MEGA pixels. Still an interesting idea and worth a watch.
Giovanni and Maria Laura pointed me to this blog on general tech stuff, which has a thing for alternative interfaces. Nothing new to me, but I don't think I've posted all the videos they have up there, so worth a look. Not maintained by a scientist, and most of the videos are posted as new, but really old. A few nice demos of the wonky "EEG" systems (I use quotes when I mention EEG and those consumer devices with a single dry electrode). The below video is a must-see, and was caught by this site.