There is the PIR sensor, which is a motion sensor. But not sure if it is applicable to your project.
If the transmitter will be small, maybe you can use a LDR, which is a resistor that varies with light. It may be faced down, so whenever it is lifted, there will be light and the resistance will varie. But that would not work at night..
For transmitting the signal, Zigbee it is an option, but not a very cheap one. Maybe you could use the small 433MHz modules. Is the use of a microcontroller possible?