The CORE TRANSFORMER
9. The CORE TRANSFORMER ($19.99 for the tube/$29.99 for tube and DVD; coretransformer.tv)
Why we like it: It may look like another overhyped TV exercise product, but this unique—and economical—fitness tool definitely burns calories. The X-shaped stretch cord device straps onto both of your feet and hands, adding resistance to your arms and legs, no matter what direction you move them (forward, backward, to the side, and so on). The DVD offers three intense routines—ranging from 20, 40, to 60 minutes long—but we found it was just as effective at making many yoga, Pilates, and core training exercises a lot more challenging and effective.