As a paranoid Android I have not been stupid enough to plug it into any computer, but we do plug it into a 12V cigarette lighter connection in the motor home or car.
Why is it brilliant!
So, in a motorhome you will typically have a gas burner hob on which you can boil water, say in a kettle to make a hot cup of tea, coffee or some other drink.
The trouble is that unless you have a Microwave, and that means an AC power connection, and that means parked at a campsite, well you cannot reheat the drink once in your cup.
[NB: there are some other solutions ranging from a Generator .. !!, to an inverter driving an electric cup heater .. longwinded, listed for completeness here but not in any way comparable in terms of price or usefulness]
Well it is possible.
First the mug is double skinned, vacuum, like a thermos. This means that hot drinks inside tend to stay warm, even allowing for the metal construction.
But as the drink cools the idea is that you plug the unit into a car cigarette lighter and it really not only keeps the drink warm but gets it piping hot again.
The only slight issue is that the electrical connection point is not waterproofed so be careful whilst washing the mug clean.
Other than that absolutely great, and drum roll ... about 15 Zloty meaning about 3 GBP all in.
Now that is a bargain. Previously we had used the IKEA Hemlig mug, but this is so much better (i.e. the USB charging)