As I noticed when I went to vote the other week in the UK General Election. All the ballots are numbered and your voter id is noted down and cross-referenced to the ballot you are handed. I had to double-check the implications of this after I'd voted and sure enough, it's a 'well known fact' in certain circles : "The use of numbered ballots makes it possible, given access to the relevant documents, to identify who has voted for whom, and there are many accounts of this being done regularly by the authorities in the United Kingdom, especially by the police and Special Branch to identify voters for fringe candidates". http://en.wikipedia.org/wiki/S...

OK, first caveat - this is a UK-based solution, so YMMV if using it abroad...

https://www.alertme.com/how-we-do-it/products-and-services/smart-monitoring/

Subscription is £5 per month ($8?). You have to buy a basic starter pack that contains several motion sensors and contact sensors. Comes with an internet-enabled hub that communicates with their servers to send alerts and receive instructions via their web interface. Also has a SIM and inbuilt battery for sending SMS alerts is the power / internet gets cut. You can also buy various extras such as a UK plugs that you can control via the web interface and therefore dictate when they have power.

I've been using for about 5 years now and am reasonably happy with it.