Your best bet is to buy something on ebay from China. They are cheap -under a hundred bucks, not a brand name item. The great thing about china is that you get all the bells and whistles and more for a great price.
These home security alarms come with normally closed and normally open switches that transmit to the main board when triggered, which can also be programed to turn on a security camera that also transmits to your phone over the net. They also come with sound and motion activated switches. The main board contains a dialer which uses a sim card. The dialer calls your cell phone when any switch is triggered. All switches have an antenna, but you can try to improvise something if you want to hide the antenna/switch. You can activate or deactivate the alarm, turn on or turn off devices attached to the alarm from your phone.The only problem is that it is easier to read Chinese than the "English" instructions but with common sense it is not difficult to set up.
They also sell dvr camera systems (cheap also) that record 24/7/363. You can connect a wired or wireless hidden camera to it. They also sell ultra small wide angle dvr spy cameras (cheap about 70.00) from china The battery lasts about 8 hours or you can connect to a power supply 24/7. They record to a micro sd card.