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My parents got this a while ago and when we moved they got another one for the new house. It measures your home oil tank and sends a signal to the remove monitor to tell you how much oil you have left. It will sounds alarm when you should order oil and just plugs into any outlet in the house.
They go for around $140 on Amazon and will save you money in the long run as regular oil delivery usually costs more than just calling as you need oil. At least in our area, we have a supplier that's a lot cheaper than the scheduled services.
The Beckett Rocket is a wireless ultrasonic fuel level monitor complete kit which includes Receiver, Transmitter, 2inch NPT adapter, 2 mounting screws, and instructions.
Installation was real simple and took us around 15 minutes. You unscrew the cap on the top of the tank and screw the new cap on with the remote monitor. Set a few dip switches on the meter for the size and shape of your tank and that's it!
The remote uses a lithium battery but after five years or so it is still going. It's also sold under the brand name Apollo and you can see it in action in this video:
If you want to save a little money in the long run and not have to crawl in awkward spots of your basement, this is a very handy gadget.