The HausNet oil gauge sensor uses an inexpensive camera (e.g. ESPHome + ESP32-CAM) to capture images of the typical oil float gauge, and, using Machine Learning to extract the float level from the image. Documentation can be found here: IndiCam - HausNet Documentation
Note that this is a Beta, best suited for users who are prepared to get their hands dirty. The primary purpose of the beta is to expose the Machine Learning algorithm to more types of gauges, so there may be an initial learning period where the algorithm catches up to new gauge data.
Installation is through HACS, and details can be found in the docs.
Give it a spin, and let me know if there are any questions.