I'm not sure that I understand the need for a level detector. In this case they had a double indication of zero pressure from two separate sensors. There was talk about "splash lubrication" but its not a piston engine! If you have a large volume of oil sitting in the sump not getting pumped round, how is that any better than having no oil at all? - and so how does a level detector help you?
I believe geneman makes a quite valid point re having level sensors. Have had two occasions where the MGB dumped all the oil.
In the first (205) the cause was a split "O" ring seal, and of course have no idea how long it took before the simultaneous red light and zero oil pressure. Flew on for approx 15 minutes.
The second occasion (212) the rotor brake drive fractured leaving the disc lying on the cabin roof and dropping the bevel gear and shaft into the guts of the MGB, where it bounced around tearing up gear wheels but continuing to run OK. It took approx 6 minutes for the MGB to empty itself.
I ask, would it not be nice know what was happening to the level? May go a long way towards your decision making, rather than waiting for caution lights and pressure indications. Finding yourself suddenly with zero pressure (say) in the cruise at 9,000 is going to eat up lot of that 11 minutes (as demonstrated) getting to the ground/water.
Buys you time.
Our fixed wing brothers/sister have level indicators on many of their aircraft, so it ain't rocket science.