Both Ferraris wheel and electronic meters are designed not to read below a specified starting current, which is set out in the specifications. They typically start at something like 10W, although the start point varies from place to place. This feature is intended to eliminate any tendency to creep under no load conditions, and slowly record usage when there is no load at all.
I wonder how many have observed this and tried to profit from this source of "free energy"
Well, if the only appliance in the house which is on is, say, a phone charger it won't be charged. Its hard to get much value out of loads below the start current, though. You might if you could charge a storage system at a steady 7 or 8 watts, 24 hours a day.
Water meters, on the other hand, do offer the ability to get useful amounts of free water. Most water meters are mechanical, and the mechanics have some stickiness. Most water is used in small bursts. Spread out your consumption over 24 hours, and you might stay below the point where the meter unsticks and records. Put the plug in the bath tub, and leave the tap dripping all day. Now you have many litres for free. This is a problem in some parts of the world, where families can obtain most of the water they need without it being recorded.