Andy Rubin said Wednesday that next week he will spill the beans on his secretive startup, Essential. But he's already tipped his hand a bit.A couple hours after Rubin's tweet, Essential posted a silhouette image of what looks like a smartphone and a big antenna bump. But the company's followers were not stumped. They zoomed in and were able to make out a lens. Combined with an earlier image that Rubin had tweeted, many deduced that it was a 360-degree camera attached to the company's still-unannounced phone.That silhouette reminded me of another attachment to another Andy Rubin-made smartphone — the camera that adorned the early Danger Hiptop. The first camera took postage-stamp size images (120 pixels by 90 pixels) and plugged into the phone's headphone jack.