Feature Categories System Apps System level access. Ex. Carrier or manufacturer. Premium Apps SMS Apps requesting premium access and features. ex. Hidden text messaging. Anti-spam Apps SMS apps that block messages from regular messsaging and other apps Plugin Apps SMS/MMS preprocessing for special features. Autoresponder Apps SMS apps with a autoresponding feature. SMS Messaging Apps Standard text messaging apps Backup and Recovery Apps SMS apps that require full access to the SMS database. Observer Apps Observers will simply recieve an additional SMS_RECEIVED broadcast.