The grenade-size SRS-XB10 is the smallest and most basic of the new speakers in Sony's line of Extra Bass Bluetooth speakers. At this size "extra bass" might be a stretch, but it does have a bit more punch than many competitors.
The Sony SRS-XB10 is an ultracompact, canister-style Bluetooth speaker that's water-resistant, with good battery life (16 hours) and speakerphone capabilities; The speaker sounds decent enough for its size and its strap converts into a stand to prop the speaker up horizontally
The soft-but-tough finish attracts some dust; should cost less than $50