First off, always listen to Peggy Hall. But another solid alternative is Gobius sensors. They make two different types of bluetooth connected sensors:
- Gobius Pro: Ultrasound, mounts on vertical tank sides and signals whether tank is filled to the level of the sensor. You need multiple sensors to judge varying levels, though I've previously just mounted one on a black tank at 3/4 to signal it's time to pump out. (~$199)
- Gobius C: Radar, mounted on top of tank and provides the actual level of contents in the tank. Configurable with variable geometry tanks. (~$350)
I have used the Gobius Pro and found it low power, very reliable, and easy to install (just clip the power wires to your existing tank sensor and connect to the Gobius sensor). I'll be mounting the Gobius C this winter on my current boat on my fuel tank. You can always view the sensor on an app on your phone (or tablet, etc.). There may also be a way to hook the Gobius C into your tank gauge, but I have yet to dig into that so don't take that as gospel.