I remember that several years ago the Danish television channel DR showed a news spot by journalist Morten Hartkorn on 1 April where the story was suspiciously strange. The clever April’s fool joke here was that the story was actually real and (if I remember correctly) a TV critics fell for the joke and thought it was an April’s fool joke (to the schadenfreude of other TV critics).For the April’s fool joke of the year 2011 we have heard of Google Motion, a system that let a user interact with an email program by gestures and postures in front of the computer. The cleverness in Google’s joke may be that the knew that this was likely that people (nerds) could implement the joke. In didn’t take long. Already on 1 April postdoctoral researcher Evan Suma had uploaded a video demonstrating such a system. Suma and his folks used the Microsoft Kinect. It would probably be harder to implement such a system with a standard PC/smartphone camera. Emailing may not be the obvious choice for body motion control. Typically you need to type in longer text which is yet best handled with a keyboard. I think the control of a television might be a more appropriate application. Typically you only need to change channel and turn up and down for the volume. You would need camera of the Kinect type on the television set and body motion recognition software. I am not sure I want such a system in my house. If the television set has Internet connection and gets hacked the perpetrator can broadcast your living or bed room to the curiosity of the world via something like Bambuser. In Denmark one of the newspaper carried a story on ultrasonography with a mobil phone. Given that modern smartphones have so many trasducers and receivers (microphone, loadspeaker, wifi, mobil antenna, gyroscope, accelerometer, GPS, vibration, camera, screen, did I forget any?) it is interesting to ask how far we are from implementing this April’s fool joke. AFAIK you will need a piezoelectric crystal as the Ultrasonic transceiver. I am not too familiar with the issues around the design of such things but my guess is that it would not be impossible to fit a transceiver inside the mobilphone, but there might be problems with the vibrations it emits to the entire mobil phone. Back in 2009 American researcher reported they could do ultrasonography with a mobil phone. But this was with an external USB transceiver. There are commercial USB systems, see InNovaSound. FDA-approved they are quite expensive with a price of well more than 1000 American dollars as far as I can determine, but it seems that the price is falling. With non-FDA-approved mass-production we see in the mobil phone industry the inclusion of ultrasonography into modern smartphones seems to be a possibility.