get a dog, ours find's cats all the time he has brought home a couple now and then
haha funny
, but probably the cheapest way
unfortunately there are many posts on here like capannini's, where the poster just doesnt realise the complexity of what they are asking.
Capannini, for a unit like you are asking for its neither going to be cheap nor small.
1) to have a receiver and transmitter and batterypack to accomodate what you are wanting, its going to be the same or larger size than the ones already on the market
2) sooo the cat ( other animal) goes missing and you send out the activation TX to the receiver. you dont get a response...
is the reason ....
a) ... the receiver is out of range of your transmitter ?
b) ... the gsm TX out of range of a local cellular tower?
c) ... the battery gone flat ?
d) ... an electronic fault in the unit?
e ... all of the above ?
you will have no way of knowing which is the reason.
This is the EXACT reason, as posted earlier, that animals are microchipped then the owners can be contacted when the animal is found by some one. So so much easier and cheaper
Dave