There are alarms that shut off if large amounts of water flow through a pipe when the alarm is set: Avoids washer hoses or frozen pipes from running undetected when you are on vacation. That type wouldn't help you.

There are others that detect moisture with a probe of some sort and are specific to the area. You would need a probe behind the fridge, under the sink, under the dishwasher, etc.

Re: Brazilian Cherry. Make sure that you are replacing it with sustainable harvested wood (LEED - MR7 designation).

Do a Google search for "Leak Frog." It's a silly-looking, green plastic frog that takes a battery. There are 2 contacts on the bottom and, when there is the slightest amount of water on the floor, it completes a circuit and sounds an alarm. You should be able to find this item for about $10. For some reason, they are $50 on Amazon, but mine was much cheaper and it works great.

Thanks. I'll look for one today.

My water heater is located in my attic. I have a drain pan under it but just to ensure I have no problems, I installed a automatic shut off valve. It runs off of a standard 110 outlet and it also has a battery back-up. You install the device on your inlet side to the tank. There is a sensor that you place in the pan under the water heater. Should a single drop of water hit the sensor, it immediately shuts the water supply to the water heater off. It does work. About a year ago, I wanted to remove a plastic check valve in the water heater. I forgot to move the sensor and when a few drops hit it, the valve closed. Once closed, there is a button to reset the valve. There are also ones for washers and refrigertors.

Here is a link that might be useful: Auto shut off valve for Water Heater

The problem with very small but long term leaks is they may never touch a sensor to trigger an alarm.

If the water never made it from under the refrigerator the 'frog alarm' would never have gone off.

Use copper tubing for refrigerator lines (and ditch the 'saddle valve' while you are at it).