We have an alarm on our house that will ring up my and my husband's mobile phone, but this works from mains power (and needs a phone line to work).
Is it not possible for you to borrow a dog (the bigger the better) and lie in wait for them? My guess is that if they're not sure if the dog is there or not, they'll steer clear.
There's nothing like the sight of a dog's tonsils, surrounded by sharp yellow teeth to get the little bu88ers running like Usain Bolt.
You can get small cameras that are powered by batteries, but the pictures aren't that good, and my guess is that lighting would be an issue. You could try just putting up the CCTV warning signs, and see if that has any effect. A phone call to your local Crime Prevention Officer (yes, they do still have these in most forces) may help, they can provide suggestions and if all else fails can go into local schools to ask politely for the blighters to stop. They can also advise on marking your property, in case it turns up on ebay or a local car boot sale, it will PROVE you still own the items (especially if you're reporting ALL thefts, not matter how small).