This is the transmission part of the UD-Alert

It's based on an Attiny85 running at 1Mhz on his internal oscillator. A cheap 433Mhz RF module for the wireless transmission in the house,a end switch and a CR2032 battery.

The circuit is in normal state in sleep mode, and use about 0.14uA. When the switch is activated, it generates an interrupt, and the Attiny is powering up the RF module over Pb3 and starts transmitting a code, with the help of the RCSwitch library, over Pb4. In this short moment, it pulls 0.7mA. I think on normal use, the battery should be good for 5-8 years. The RCSwitch library is for cheap power plugs, but it's exactly what I need for this project. The  modules i used can be found  here. 

I can not tell you in meters, what distance they transmit, but it works through our house made of concrete over the 3 floors. 

The receiver Part. You can add a display, but I think some kind of pager design will be more than enough.

This part is under construction. for the moment, I use my Arduino QP project