I don't currently have any of the little odd shaped tanks, jars,etc. but it seemed like these being flexible and coming in lots of sizes and wattage, they might be something that could be bent around the back side of some of the really odd shapes. Or using several small wattage like 8 watt added together they might be placed in several spots with something as simple as plywood to attach them as well as insulate. I thought they might really beat those big old 25 watt heaters without thermostats sticking out in the tanks as we could better size them for the smallest tanks that don't need a full 25 watt.
The first three probes failed between three months and a year from the start. It seems there are different types of sealant used, some better than others so I now just put them in straws as a routine as it also helps me in hiding/controlling the wire and placement. Some points that make a difference is that I do keep plenty of circulation in the tanks as it does make the heat more uniform but also the CO2, etc. so when I add a probe, I often lay it flat in a corner and the straw serves to make the wire go straight up without gobbing silicone too far. The last couple, I have found I can get away with just lowering the water level and using super glue in the corner. What I do watch for is letting water go down the straw so that the whole idea is wasted, so I force a bit of silicone in the top end to seal against any water splash or spills.
I've learned to expect my screwups!!