Musicians waste too much time dealing with annoying metronomes, tuners, wonky bandmates, and battered ears. Soundbrenner Core ($199) is a 4-in-1 wearable that seeks to banish such problems. Its decibel meter notifies you when your ears are getting pummelled. The face becomes a magnetic tuner, for guitars, violins and ukuleles. And then there’s the metronome. This hits your wrist with seven times the force of other smartwatches, and you can adjust tempo right from the watch face. Going freeform? Tap out a beat (or just train your inner clock when on the Tube). Rubbish bandmates? Give them all a Soundbrenner Core, sync, and keep everyone in time. And it’s also a watch, so you’ll be in time for gigs in every sense.