As bombs blasted Baghdad last week, dozens of cell phones in China buzzed with messages about where to stage an anti-war protest. In Cairo, activists tapped out text messages to summon 5,000 demonstrators to a central square, and in San Francisco, technophiles beamed live footage from protests to anti-war Web sites. Prohibitively expensive only a few years ago, gadgets ranging from the cell phone to the mini digital video camera simplify protests from Brussels to Manila.