GPS to GPS communication

My normal caveat #1: this may already exist. The idea involves taking a regular GPS unit but adding a 2-way radio that (among other things) allows the GPS to communicate with other units. This means your GPS can relay its route to other GPS units so that your friends can see exactly where you are and where you are going. For example, if you're backpacking and part of your group falls behind, they can still see where you went and follow your exact route.

Map scrolling using motion sensors

Rather than pushing arrow buttons to scroll a map left, right, up, or down, a motion sensitive device could be tilted in the direction the user wants to scroll. The larger the tilt, the faster the scroll. Shaking the device could restore the display to the starting point or user's current location.

Fingerprints for recommendations

A number of audio fingerprint technologies exist today and are used for things like radio monitoring, copyright filtering, and content identification (e.g. Shazam). To over simplify, these technologies work by generating a fingerprint from acoustic information of a track, and then determining whether there is a fingerprint of known content that is similar enough within a confidence threshold that the track can be reliably identified. This is probably already being done (I haven't read up on the literature) but it seems to me that you might end up with a half-decent recommendation engine if you ignore the high confidence hits and instead look at the medium-low confidence hits (aka near misses). Because recommendation engines can be pre-generated and speed is not a problem, you could only pair songs that had multiple "near misses" at different points in time.

Sythesizing high-resolution audio...

I don't remember enough information theory to know whether this is even possible, but I was wondering whether one could create a high(er)-resolution audio recording from multiple low resolution sources. Specifically, imagine a bunch of fans recording a concert using the video cameras on their cell phones. The resulting audio would be pretty lousy on a per-recording basis, but if you put them all together, would it be possible to subtract out the crowd noise and reproduce a higher fidelity version? Theoretically, it seems that the same signal processing techniques (if they exist) could be used to take multiple low resolution images and synthesize a higher resolution image.

Crowd music

A device with a microphone, speaker, and accelerometer. The device's software is programmed with basic music rules (rhythm, melody, musical keys, harmonies, etc.). A single device will make random melodic music in a single voice to the beat that you shake it. Additional devices listen to the music being made and make something complementary in the appropriate key, also to the rhythm to which they are shaken. The software will compensate for slightly out-of-sync rhythms, but will allow off-beats, double beats, and other beats that would sound complementary. Each device will pick an octave and voice so that the combined music is comprised of interesting and musically appropriate layers.

A collection of these devices should make interesting music when "played" together.

A phone service that...

A service that you can call and vocally give the name of a Wikipedia entry and have it read the entry to you so that you can get information about different topics from your phone. Would require basic navigation for following links. The tone of voice might vary to indicate a link, the speaker might vary, or the system might say "link".

Digital sheet music for concerts

Here's the idea: sheet music on a digital display (LCD, OLED, eInk, etc.) instead of on paper. The unit listens to what you are playing using digital fingerprints of the music and automatically turns the page for you when you get to the right spot. Could show you where you are in real time (no more losing your place, if anyone actually has that problem), and would let you skip around.