This just happened to me. We go over to my friends house for Mommy day weekend. Fix up some bobs to throw on the barbie and halfway through, the propane runs out. No biggie just ended up throwing them in the oven to finish up, but it could of been much worse. With Smart GasWatch ($35) this would have never happened. Smart GasWatch is a propane tank scale with a gas level indicator that connects to your phone via bluetooth. It tells you how much propane you have left and lets you know when you’re running low. It even gives you an estimated cooking time left based on an average BTU output of 40K BTU/hour. No more surprises. The app is compatible with iOS and Android phones. The crowdfunding campaign is going on right now over at Indiegogo.