I have a Basement Watchdog.
Pro
No failure of electronics yet.
Works fine IF the battery is in good condition.
Con
Pump is undersized. If you have a power outage and a shitload of rain, it won't keep up. Just talked to someone who had their basement flood because the backup pump worked fine, but couldn't keep up.
Its battery charger will constantly cook the water out of your battery. Plan on adding water every month. Lots of it. I keep a gallon of distilled water and an automotive battery filler jug handy. I go through a gallon and a half a year.
Float voltage is around 13.7, charging voltage is about 15.8. Too high in my opinion. The power supply that comes with it is unregulated, so voltages vary.
Beeps with any power glitch that has to be manually reset to silence it.
Beeps to let you know there is a power failure. I can figure that out on my own, thanks.
You have to figure out when your battery is at the end of its life. Usually 4 years.
Don't get an Ace in the Hole. There is a component on the circuit board that fails annually rendering it inoperative.