8) Wanna be rappers
Can create a personalized rap group. Have programmed in some poetry that works well to a definate beat and sounds "cool." This "box" will interact with the user as they slow down or speed up, or could be set to keep an unyielding beat.

2. Digital Recorder trigger kit
This would be a digital sound recorder, a speaker, and a kit of triggers and cables for kids to set up gags of various sorts. Triggers could include motion detectors (to work as alarms), piesoelectric sensors (digital whoopee cushion), timers, IR remote control, sound sensor (telling people to "Ssshhh"), light sensor, etc. Could include prerecorded sounds from action movies, funny sound effects, and a cable to record sounds downloaded from the net. The kit could also include ways to disguise the gear as coffee mugs, picture frames, etc.

3. musical skipping rope.

when i was a kid there were a lot of skipping games that used to be played during school breaks. This would be a standard skipping rope that had a small loudspeaker and a recording of the music and perhaps lyrics with and without the rules as alternatives to be selected. There were/are a lot of these games, and as i recall each school had its own local knowledge bank, which the skipping rope could increase. Possibly also with the ability to record.

10. instrument trainer/accompaniest.

follows in the ground breaking steps of "silento brasso" (a japanese  mute for brass instruments which considerably quietens the sound, but recreates the actual sound of the instrument through a pair of headphones for the player). This would be an intelligent music trainer and also provide accompanying instruments to simulate playing in a group. You can buy cdroms that sort of provide this for musical instruments, but this would have intelligence and would provide training exercises and and an accompaniest as you play. Version 10.3 would detect egregious mistakes and suggest exercises to resolve them.

Audio Spotlight Jr. - A little megaphone that "throws" your voice across the room. Appeals to the desire in all of us to play ventriloquist.

2. You Are The Star: Karaoke+. The 'base' unit would be a microphone and a speaker unit you would place on the floor of your living room, amplifying your voice, but the 'hook' is that you could get additional, disconnected units that modified or augmented the behavior of the system: Additional speakers, perhaps that do reverb or some kind of percussion overlay. A colored light that pans and swivels to track you around your living room. A networked node that brought in additional content from the internet or connected you to others singing the same song throughout the world for ensemble numbers.

3. Travel Echo. A gps enabled device that you carry while travelling. It records snippets of audio in it's environment and uploads them to some central database. Later when someone with a similar device comes to that same spot, they hear an echo of those who have come before them. I think the trick here would be in not making things too easy. It should not be possible to play the audio for some arbitrary location without actually going there. It should also try and avoid people specifically recording a certain something but rather wait for 'candid' audio moments.

--Personal Music Box
You can download the music you like and program the box to play it according to different parameters... can be environmental, emotional, etc.

Really magic 8 ball
listens to your questions and reconfigures meaningful answers

- card with voice chip for passing secret messages, perhaps via IR

- sound splotlight for secret messages at a distance, like Star Trek