Vacation snapshots are nice, but wouldn´t they be nicer if you could swipe your cellphone over them to retrieve video, sound files and captions? That´s the idea behind the Memory Spot, an adhesive chip in development at Hewlett-Packard´s Bristol, England, facility. The stamp-like memory device comes in two sizes, 1.4 or 2 millimeters square. Affixed to a photo or document, it can store and transfer up to four megabytes of data, enough for a short video or a couple songs.