You don't have to buy it, but it is reality. You may have owned countless devices over the years but I am guessing you haven't designed or put into manufacturing any of those devices. The OP asked if there was any benefit for the consumer and I explained at least one. Yes, the manufacturers also...
Send it back to First Alert and tell them it was giving a false positive reading. If it is less than 5 years old they will likely just send you a new one.
I love my Kershaw Chive. It is the perfect size for clipping in a front pocket and stays out of the way until you need it. And the spring assist means when you need it, it is out quickly.
Probably the biggest benefit to the consumer is keeping the up fronts costs down. It may not seem like it at first glance, but creating a gadget with a removable battery is considerably more complicated than a non-removable battery. Latches, hooks, and swivels all increase the tooling costs for...
As long as the LEDs are of the same type, vintage and with similar usage history, any minor differences in voltage drop can be taken up by the series limiting resistors--which you should probably have in-line anyway.
I would agree that Fluke is generally the industry standard for EEs and techs--their 8X series is probably used by more professional labs than any other DMM. However, I would also suggest that most of the models Fluke sells will be way overkill (and more expensive) for most functions required by...
In any generic electrical system, maximum power transmission occurs only when the source and the load are at matched impedances, not when the load is zero. It is an important but critical distinction because no source will have a zero internal resistance, even for low frequency systems.