Put so many together in a small space and you'll incur in more issues. This might be huge in the future, but for now just a cool concept.

10mA @1.5 volts is plenty for all sorts of things! Just two of those things and you've got 10mA @3V which is more than enough to power a Bluetooth Low Energy microcontroller and some occasionally-lit LEDs, displays, sensors, buttons, etc.

Simple, real-world example: Nest sells these remote temperature sensors that you can place around your home to use any given location (e.g. your living room) as the place where you want the thermostat temperature setting to apply. They take a 3V CR123A battery that needs to be replaced about every 3 years.

A CR123A battery only holds about ~2.4 watt-hours of power. That's 2500 milliwatt-hours or 250 hours of 10mW @3V. That means the Nest temperature sensor uses about 0.0095mA of current (@3V). In reality it uses a lot more than that; it just stays in a sleep state nearly all of the time and only powers up every few minutes when it needs to take a temperature reading and send it to the thermostat.

TL;DR: Just one or two of these energy harvesting devices could power a Nest temperature sensor forever (assuming they don't wear out or lose much efficiency over time).

There's zillions of low-power devices that today use batteries (that often corrode and need to replaced every few years even if they might not run out of power) that could be powered by these humidity power harvesting devices. It could change low-power engineering forever!