At the tiny scale of a single cell, measuring movements isn’t easy. So the researchers wanted to find a way to get the clearest signal about a particular environmental condition—in this case, humidity—based on how much a cell moves in response to it. The researchers chose a particularly sensitive kind of cell, a spore of the bacterium Bacillus, and placed two quantum dots on its cell membrane. Quantum dots are tiny conductors that can efficiently transfer signals from one medium to another.

The researchers attached electrodes to either end of the spore and measured the dots’ conductivity; when the humidity was lower, the spore would contract and bring the quantum dots closer, which would create a spike in the conductivity reading. Each time the researchers changed the humidity around the spore, they saw a clear change in the readings, with a response rate 10 times faster than the most advanced water-absorbing sensors, they said.

Such rapid and sensitive humidity readings could be useful for conditions where changes in humidity could spell disaster, like to detect leaks in space.

Robert Heinlein thought about this problem. In his 1948 short story Gentlemen, Be Seated, he described life in a lunar habitat. And the inevitable air leaks.

There were perhaps a dozen bladder-like objects in the tunnel, the size and shape of toy balloons. They seemed to displace exactly their own weight of air; they floated without displaying much tendency to rise or settle. Konski batted one out of his way and answered me before I could ask.

"This piece of tunnel was pressurized today," he told me.

"These tag-alongs search out stray leaks. They're sticky inside. They get sucked up against a leak, break, and the goo gets sucked in, freezes and seals the leak."
(Read more about Heinlein's tag-alongs)

As far as I know, the first sf writer to combine electronic and tiny portions of living systems to create new products was Philip K. Dick.

As far as every day consumer products are concerned, you can't beat the Ampek F-a2 Recording System:

Nat Flieger reflexively poured water into a cup and fed the living protoplasm incorporated into the Ampek F-a2 recording system which he kept in his office; the Ganymedean life form did not experience pain and had not yet objected to being made over into a portion of an electronic system... neurologically it was primitive, but as an auditory receptor it was unexcelled.

(Read more about Dick's Ampek F-a2 Recording System)

Readers in their second decade of enjoying Technovelgy.com may recall a very similar idea from 2005 - 'Cellborg' Humidity Gauge First Bacterial Cyborg .