Now that indoor mapping solutions (see link) are already
becoming available, practically everyone has been
about the potential of this for commerce -- i.e.
malls and store isles.
But the real potential is being lost -- the real potential is
finding things you've
lost at home.
Create a website/app that uses the mapped layout of as
discussed in the link, and then locates and stores, for
display, on an ongoing basis, things that transmit either
RF, Bluetooth, WiFi or cell signal, such that even if they
are powered off, their LAST known location is available.
I suppose an indoor ultrasound/radar solution might be
interesting as well (Star Trek scanner style).