OK, here's a challenge. Build a tool to assist with short term memory loss. The idea is this:

• You go to the top of the stairs to do something
• You get there, and wonder what you were there for

It'd be neat if you could do this:

• Wear a simple looking pedant, which was a short term memory assistive device
  
• Simply mutter to yourself what you're doing
• When you forget what you're doing you press/tap a button & hear a repeat of the last muttering
• Press it again in rapid succession, and you get the one before, and so on. (giving you context "what was I doing before...")
  
• Aesthetically, it would be nice if the device looked like a pedant or similar.
• The playback/recording could be a simple earpiece/microphone (ala mobile phone handsfree).
• It should be sufficiently low power to run happily for as much of a day or more as possible.

Technologically this sounds like it should be really quite simple & trivial to make today.

• Now here's the thing - you could do this today with a notebook & pencil hanging from a necklace - except that you replace muttering with scribbling, and pressing a button with looking at the notebook. Or perhaps hanging a dictaphone round your neck and remembering to hit "record" every time you say something.
• However, not everyone who might find such a thing useful (ie most of us when we get older) would be comfortable with the notebook on a necklace or dictapone on a necklace approach, but may find a short-term memory pendant assist socially acceptable.

So, the challenge is - could you make this today (almost certainly), and given that, how would you do so? This isn't entirely a thought experiment - people with alzheimers may find such a beast useful, and simply having to press a button to hear what you were doing and double tapping to hear what you were doing is probably something learnable. (maybe, dunno in that context really)

I suppose in a way it's a bit like an personal audio twitter with absolutely minimal interface with zero connectivity.

Incidentaly, imagine what you could use such a device for beyond this...