Here is a simple and cheap DIY way of being alerted if the float switch or pump fails on the shower sump. I am sure all of you have found the sump overflowed and filled a substantial amount of water into the bilge at some point. Only way one notices is the shower does not drain as well so one tends to verify however usually way too late and most likely after multiple showers. This will prevent this from going unnoticed. a simple small float switch installed into the cover of the sump, a small piezo buzzer and hook up to the same 12v power supplying your sump bilge pump. Loud enough to be heard under the floor. The piezo draws only a few milliamps so no issue connecting directly to the float.

Float switch. https://www.amazon.ca/dp/B08122CS3N?psc=1&ref=ppx_yo2ov_dt_b_product_details

Piezo Buzzer. https://www.amazon.ca/dp/B07HDYSY1V?psc=1&ref=ppx_yo2ov_dt_b_product_details

I did add a waterproof connector however this is not required.