Airconditioner condenser protection?

Wondering what others have done to secure their AC units from copper thieves. Have seen several somewhat isolated houses recently with stolen AC units.

Most A/C compressor coils here are aluminum now.

Personally, I haven't done anything to secure my AC unit.  It just seems unlikely that anyone will try to steal it. That sort of theft hasn't occurred in my area.  Risk could be higher elsewhere, of course.  But I'm happy to rely on homeowner's insurance to cover me in the event that it does get stolen. 
 
If you really want to protect it, a couple of ideas come to mind. 
 
- Add a wired alarm contact on the access cover to the unit.  If they cut the wire or open the access cover, it will trigger the alarm.  With a little luck, the police will get there before they can cart it away.
 
- Physically secure the compressor to the ground (e.g. a concrete pad or footing) with tamper proof security anchors.

Lock your disconnect switch box on so that the things is always alive. That should slow down most non-electrical people. Makesure there is a red caution - live  sticker on the unit.
 
Put 75% of a security system in your house. That involves putting the very visible coloured and visible "Protected by ....." decals up that security companies use to stop most would-be burglaries. They are cheap and  good as a deterrent. Make sure one by the A/C is visible.

Disconnects don't stop them. Easy enough to get around and remove all the components worth money. Hell, it's easy enough with a bolt cutter or battery cutoff wheel to fix that and get the rest.
 
I've seen them strip a house covered in aluminum siding, pull gutters and even cables out of underground conduit
 
http://www.thewhip.co/
 
Supervise the pressure on the unit and be done. Downside is the EOLR values are posted and they say to NOT glue or secure the fittings.

Just make the neighbor's condenser look more appealing.  Both neighbor's at a previous house had theirs swiped a couple times, but not ours.  I like to attribute that to the holly bushes I planted around them.  
 
On the construction side, every project I've been involved with over the past decade or so has had some type of theft incident.  I've started including 24-7 security or video surveillance as a requirement in all of our architectural specifications just so i can't get pinned for the the cost of the damage it causes when they rip the walls up.  What's nuts is that often times the thieves look right at the cameras and smile...and still don't get caught.