It appears that you forgot to end your sentence with `/s`. The first time I read it, I did not see this as sarcasm, and so did not understand why @superpie responded to you the way she did.

Now reading your comment again after a few days, it's clear that it's sarcasm. So it would've really helped the "slow" people, like myself, to see the sarcasm right away, and respond to your real concern/intent.

I guess the lesson is, people on the internet can't read your facial expressions, so make those expressions explicit by using the small cues like /s liberally :-) That's why I use this generic smiley liberally in my conversations, to show that even though I might be complaining about something, I'm in a generally happy mood, and don't want the reader to get the idea that I'm pissed, which is the default expression a reader might perceive me to be in.

Back on topic. Yes, this gadget seems useless for portable things that you actually move around quite a lot, e.g. a toddler's toys. But many products use batteries, and yet they are not moved around much, or at all, e.g. Keyboards, TV remotes (the ones that are used only to turn the TV on or off), Kitchen appliances, Game controllers, etc. This would be a great idea for those portable-but-not-usually-moved battery-powered products.

I agree with @sidpatil, though, that these should be cheaper so that the customer may want to at least consider using this product before popping in the next set of batteries. Bonus points if you can make the visible parts in different colours to match the customers' other appliances.