Get yourself a shimano internaly geared hub with their roller brake. The wheel is almost impossible to steal. In fact, I have trouble getting the wheel off when I have it on the stand. It's hard to steal for a variety of reasons.

First, it's essentially single speed, so you have to deal with the chain. While that doesn't sound very hard, it is because of the second reason.
Second, the internally geared hub has a cable that runs down the right chainstay, like any derailleur, except it's a straight, short cable housing. It's just the nature of the hub. That straight short housing does a VERY good job at keeping that side of the wheel held back in it's dropout. Now, if you think about that for a few seconds, that means it's very difficult to remove the chain since you can't simply move the wheel forward.

Removing the wheel with those two things involves a intricate dance of moving the wheel forward enough to get a tiny bit of play in the chain, then carefully taking it off of the front chainring. Then you pull the wheel back and remove the housing from the braze on. Now, the second part of that can be made more of a pain if you use the single speed adjusters (tiny screws) screwed into the back of the dropout. If you actually adjust those to where they contact the axle, like you should, that actually means you have to loosen the right one before pulling the wheel back enough to allow removal of the small housing. Not ONLY that, but you also have to remove the actual shift cable from the hub because it'll catch if you try to pull the wheel back with it still attached. That involves having a small 2mm allen (or anything just as small) to act as a lever to lever the hub around, providing cable looseness that allows you to disconnect the cable from the hub.

Now, if that weren't all a pain in itself. The rollerbrake adds ANOTHER small housing to the LEFT SIDE chain stay. This one is slightly easier to deal with, but only because I'm the one who installed it. It has an odd quick-release that most people wouldn't get without being shown. It also has a "coaster brake like" attachment on that chainstay. Basically the rollerbrake has to be dealt with before anything on the drive side can be touched.

After all of that, the hub itself bolts on to the bike with 15mm nuts. I wouldn't guess that many thieves are carrying 15mm wrenches around. Allens probably, but a set of wrenches? Probably not.

All in all, it'd take FAR too long to steal that rear wheel and it'd be far too much of a pain to steal it while the bike is attached to something.

(Oh and it doesn't matter if the cables are cut, the housings are still in place so the thief would have to know to cut those specifically to allow the wheel to fall out.