There have been many attempts at bringing classic gaming to smartphones, but they all lack the most visceral part of the experience: the satisfying ka-chunk of plugging a cartridge into your console. You might get that vibe back if Japanese startup Beatrobo has its way. It's launching the Pico Cassette, a game cartridge that you plug into your phone's headphone jack. Unlike the vintage carts of yore, though, these don't actually hold games -- instead, they transmit an inaudible tone that unlocks content you've downloaded. No, it's not just a nostalgic approach to anti-piracy measures. The technology also enables saved games that sync across multiple devices, so the cartridge will feel more like your unique copy than a mere dongle.