I haven't tried anything off an electric smoker. My brother-in-law recently got the MES30 mentioned above, but I haven't had a chance to see it in action or taste its wares just yet.
But yeah, the propane running out is a risk. That's one advantage of the Maverick ET-732 remote thermometer I mentioned. If the temp is rising, you're getting a flare-up. If it's falling, you might be out of propane. It's a good way to keep an "eye" on what's going on.
I'm a homebrewer, so I just happen to have three propane tanks. So if one runs out, there's always another around. I'd highly recommend if you use a propane smoker or grill (or both) to have multiple tanks so there's always a spare.