very funny.... a full cylinder costs 15 riyals, and you would have surely used 80% of it before thinking of a refill. The left over gas is worth about 3 riyals. You want a checking device fixed to each cylinder to check how much gas is left in it? Do you have any idea how much it will increase the cost of the cylinder itself??

It would be a real good idea to have a stand by cylinder. use it until you have exhausted the first one.replace with the stand by and get a refill in place of the empty cylinder.