Critical vulnerabilities appearing in both iPhones and Android phones point to the need for third party security products.
Apparently Juniper and McAfee think so. Juniper recently announced that it was acquiring SMobile Systems for $70 million. McAfee acquired TenCube. Another product in this space is Lookout.
Finally, which operating system do you think is more secure? Do you prefer closed vs. open source? Here is a recent article from Network World discussing this issue.