the doctor in his Bonanza

With V-tailed doctor killers, there's no hope. Perhaps the laser idea
(but a 50 Watt or higher unit) could work on them. The water cooling
and huge batteries could be a problem.

We can always install FLARM and PCAS devices, neither of which up the
need for battery power too much or break the bank. $1000 US and no need
to certify every two years. Coupled with a good look out the window,
you're laughing.
The FLARM is also a GPS data logger. In Australia there's talk of
using them exclusively for contest scoring, so they know you flew with
one. At least two recent Australian competitions (at Lake Keepit and
Gawler) have been flown with FLARMS in every glider. GFA has published
results of user polls.

http://www.gfa.org.au/Docs/ops/FLARM...ls%2005-06.doc

Excellent for Europe, perhaps. Not such a good answer in, say, the
midwest of the US.

Not sure what the difference is between flying in Europe and Midwest
USA. Both crowded places with generally bad visibility.

Jim