Soon you may have to watch their favourite television shows and YouTube videos, too, as they project them onto nearby walls or commuter-train seatbacks.

Pint-size digital projectors are in the works. These devices, when plugged into cellphones and portable media players, will let consumers beam video content from their hand-held devices to the closest smooth surface-entertaining themselves, annoying their neighbours and possibly contributing to a new warning sign: No Projectors in This Area.

The microprojectors, still in prototype, use light-emitting diodes, lasers or a combination of the two to cast a display of up to 50 or 60 inches, or perhaps even wider, in darkened spaces and seven to 20 inches or so when there is ambient light.

Pocket-size device

Digital projectors were once bulky. These new models, though, are small enough to fit into the pocket of consumers who want a big-screen experience from a small-screen device. Some of the models are expected to be on the market by year-end or sooner.

Prices have yet to be announced. Matthew S Brennesholtz, an analyst at Insight Media, a marketing research firm in Norwalk, Connecticut, says he thinks the projectors will initially cost about $350, then slide down to less than $300.

Business sense

The projectors may be particularly useful for business presentations — for example, when road warriors need to show a product video to small groups.

No coordination would be needed to arrange for a screen.

Instead, a patch of wall within a cubicle or restaurant could serve for an impromptu presentation. In a pinch, a manila folder-or even a napkin-would work too.

Smart travellers

Carolina Milanesi, a research director in London for Gartner, the research firm, says she thinks the microprojectors are most likely to appeal to business travellers who, for example, could use them to beam PowerPoint shows from their smartphones.

But Milanesi is dubious about consumers using them in public, for instance, to project documents on a train seatback because they could so easily be read by others.

“I hate it even when I am on the subway and the guy next to me is reading my paper,” she said.

The projectors will first appear in free-standing, companion units to cellphones and other devices, Brennesholtz said, connected to them by standard cables.

Later, the projector modules will be directly embedded in phones, as cameras are today.

About 16 manufacturers are working on mini-projectors, he said.