I have a cheap door alarm at home (get's the job done!), it helps to warn me when my 4 year old has opened the door...
I wanted to work on a project that would reverse the affect. For example, it would sound the alarm if one side of the unit is out of range (10 foot range with urban obstacles like walls, trees, etc...), with the possibility to increase/decrease its range.
What do you guys suggest.
Thanks in advance!