Klipsch calls its Groove mini Bluetooth speaker "insanely powerful" and there's a little bit of truth to that statement -- relatively speaking, anyway.
The 4-inch tall Groove is equipped with 10 watts of power, a large 3-inch driver and two side-firing passive bass radiators. Weighing 1.7 pounds, it has some nice heft to it (though you wouldn't want to travel with it), seems durable, and has a splashproof design (IPX4 rating) that makes it suitable for outdoor use. It lists for $150 in the US. (It isn't available yet in the UK or Australia, but that price converts to about £103 and AU$211.)
Compared to other very compact Bluetooth speakers, the Groove indeed plays loud for its size and produces a surprising amount of bass. Hide it in a room and chances are people will think the sound is coming from a much larger speaker.
I like that Klipsch didn't make this a stereo speaker. As it is, these types of small portable speakers never have any stereo separation, so having a single driver is OK by me.
On the feature side, the one omission is the lack of speakerphone capabilities. That's a little strange, considering this speaker would look right at home on an office desk (I can also see it on a nightstand, in a bathroom or a kitchen), but it's hardly a deal-breaker. But it does have a pause/play button and volume controls on top of the speaker, as well as an audio input and Micro-USB charging port on the back behind a gasket that keeps out any moisture.