I saw a report by RBC Capital Markets that really captured my attention and is relevant to this discussion.  Check out this chart:

This is fascinating: 

World's Population is 6.8 Billion People

Mobile Subscribers are 5.1 Billion

There are only 394 Million Smartphone users today!!

That equates to less than 8% of all subscribers are Smartphone users.  With the cost of Android Phones quickly moving to the price of feature phones it appears obvious that Smartphone growth is in the earliest days of its infancy.  Right now it is only the wealthiest early adopters with Smartphones.  Can you imagine the installed base in a few years with continued price decreases and build out of the 3G and 4G Networks?  It is not hard to imagine several billion Smartphone Subscribers in a few years time.  From a Mobile Health perspective this is a very powerful trend.  Studies from Pew Research and others indicate that minorities and other lower income groups in the US rely on Smartphones to access the internet more than higher income groups.  As the trends towards Smartphone adoption increases installed base across all patient populations, the poor, minorities and well healed will all have the opportunity to leverage the power of these phones to increase their access to mobile healthcare applications. 

Let's look at Android Adoption rates over the first 9 quarters since its release.  This graph is courtesy of Kleiner Perkins Mary Meeker.  When you look at this chart and put this adoption rate against the total market, I believe it gives you a glimpse of where the Android Smartphone market is going, towards explosive growth.  More on the growth of Android and how it will impact the Mobile Health Market next.