Google recently announced a new user-agent for it's mobile crawler that is dedicated to smartphones. Within it's arsenal, the search engine already had a user-agent that was specific to feature phones.
The new Smartphone Googlebot-Mobile user agent is:
Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_1 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8B117 Safari/6531.22.7 (compatible; Googlebot-Mobile/2.1; +https://www.google.com/bot.html)
This system will discover URLs of websites that redirect users to smartphone and mobile content or microsites and they will change the search results to point directly to that mobile content for smartphones.
The current (main) user agents used by Google for mobile devices are:
Feature phones Googlebot-Mobile:
Smartphone Googlebot-Mobile:
The goal here is to have mobile web designers treat each user-agent exactly the way that they would treat a real human visitor (browsing by device). Google is making a focused effort to make the search result content relevant to each device.