On Sun, 31 Mar 2013 14:34:16 +0100, wrote:

Easy enough to do with one of the telephone door opening devices that
just move a plate back on a solenoid from what is otherwise a normal
front door lock keyed from both sides.

How long will any of that last outside?

Holes, chain and (weatherproof) padlock is the relaible KISS solution.

--
Cheers
Dave.