Are there any reliable, current sources of data on smartphone and cellphone usage, specifically where their usage rates, ownership, and changes in market share are compared? I've found some data for the United States, but interestingly I haven't found very much at all for countries like India, China, and countries in South America, where the numbers are much more interesting and also (I would assume) changing more rapidly. Ideally, the data would also include information about the cost of carrier plans.
Try Strategyanalytics.com. They have tons of data on cellphone/smartphone usage, installed base, operator revenue, marketshare etc. with coverage of all major regions and countries.