I've heard of a non-invasive bG meter -- the Dream Beam?

***The following information is incomplete, as another company has introduced
   a non-invasive meter for about $8000. It has been discussed in the
   newsgroup. Rumors of other non-invasive (and "non-evasive") meters abound.
   I won't be trying to keep this section up to date until the situation
   stabilizes. ***

There is at least one development project in hot pursuit of a bG monitor
which operates by shining light through flesh (through the thumbnail in one
case) and analyzing the light that passes through. Glucose doesn't affect
light much differently from many other substances in the body, so this is not
an easy task. Some field trials have been done, but the developers have a way
to go to reach acceptable accuracy. A successful product is far from
guaranteed, and may be several years away if it arrives at all.

One estimate is that such a meter might cost about US$1000. Assuming the
per-check cost is zero, this would pay for itself in 1-2 years for many
patients. Look for the insurance companies to throw up some roadblock to
achieving these savings, at least in the US.