Budding DJs and audiophiles alike will dig the new Tonium Pacemaker portable DJ system. No, it won’t jumpstart your heart (it’s just a nifty brand name), but it might get you dancing. Only slightly bigger than a cell phone, the 120GB HDD offers an auto beat-matching function and a visual beat graph to simplify song transitions. You can also bend pitch without changing tempo, and vice versa. Good for the club or a wedding or just a summer party in the backyard. $500. (www.tonium.com)    RYAN THOMAS