Google didn't go into a lot of detail about how it works; presumably it uses information from existing online services such as restaurant reviews. Allowing Google Now to access a person's location, search and calendar entries is optional, Google executives stressed, but it's bound to make some users concerned about privacy.

Jelly Bean is Google's attempt to continue the momentum behind Android. The OS had been activated in 100 million devices at this time last year; now the figure is up to 400 million, Google said. A million new Android devices are activated each day, it said, or 12 per second.

Jelly Bean also improves the voice typing function in Android, which lets users type messages and perform searches by speaking into the phone. In Ice Cream Sandwich, voice typing works only when users are online, but for Jelly Bean, Google "shrank" the speech recognition software that runs on the servers in its data center, so that it will fit into the device itself. So users will be able to type using their voice when they're offline.

Offline voice typing will be available initially for U.S. English and will be offered in other languages "soon" according to Google.

Google has improved the Android Beam function in Ice Cream Sandwich. The existing version lets users share data such as contact information by knocking two phones together, assuming they have NFC (near-field communications) capability. In Jelly Bean, that's extended to let them exchange photos and videos, and users will also be able to connect their smartphone to an external device such as a speaker by tapping the phone against it.