Every house has several meters, energy, water and gas. At least one of them has a magnetic interface. And all of them, usually, are placed in a place that doesn’t have any wire connection available. So, why not use the following suggestion to get the consume?
Battery powered pulse counter that do this:
1 - It wakes when a contact is closed.( a reed switch)
2 - Increments an user defined amount to: an total amount, and a temporary amount.
3- goes to sleep for 60 seconds. (this will determine the end of a partial consume)
4- wakeup, and test the wakeup reason: if contact, then goes to number two, else goes to the next point.
5 - Sent the values (Bluetooth, ZigBee…), reset the temporary amount, and if the the day has changed store the total amount to a non volatile memory.
6 - This should be powered by batteries,
Schematics and code woll be great.