I wired my "preliminary" bilge pump (the lowest float switch operated pump) with a $3 LED light/buzzer combo. It comes on at 1-2 inches of water in the bilge and makes an annoying beep for 10 or 11 beeps until the switch shuts off. If it kept going, or came on more than every few days, I would know that there's a problem. No need to wait for sluggish handling or secondary pump activation to see that something's amiss.
One nice thing about the buzzer is that it doesn't have to be mounted right on an already cluttered helm. Mine is on the electrical panel, so I only have to look in the companion way to see what the issue is. It is loud enough to be heard on the FB. Easy to mount right by the bilge pump breaker, which should be marked to LEAVE ON. Even better would be a tamper-proof circuit breaker cover like made for home circuit breakers.