On 07/05/2018 18:52, Rod Speed wrote:

And just typing that makes me think I should put one in the
letterbox so I get told when it gets opened, and it shouldnt
be too hard to ensure that it can't get pinched easily by having
a plate screwed in over it. Not sure if it will work tho since the
letterbox is all metal so the wifi can't easily get out. Maybe
I just need a plastic box under the letterbox with a hole in
the bottom of the letterbox that the sensor looks thru.

Cheap ultrasonic distance sensor so you know how big the package is?

Put a magnet on the flap and a reed switch to detect it opening and an
esp8266 to send the data?