Remember when data projectors were huge and expensive, and had bulbs so delicate that you were not meant to move them for half an hour after switch off?
Things are different now. At Mobile World Congress You can hold an HD projector in the palm of your hand or build it into a mobile phone. The projectors I saw were based on DLP Pico chipsets from Texas Instruments, which contain up to 2 million hinge-mounted microscopic mirrors. If you add a light source and a projection lens, you get a tiny projector.
The obvious use case is that you can turn up at an ad-hoc meeting and show photos, charts or slides on the nearest wall, instead of huddling round a laptop screen or setting up an old-style data projector.