Continuing the discussion from Availability of gas sensing devices:
This request made me think about this again. I’m no electronics engineer, but a quick Google threw up these sensors http://www.digikey.co.uk/en/product-highlight/l/littelfuse/hall-effect-sensors The 55110 looks like a useable sensor (with visible LED). Could a constantly powered (I think from previous discussions the battery would not last long) EmonTH measure the meter pulses with this? You would need a physical wire from the gas meter but I think that is a given whatever the solution.