The app gives the user the flexibility of choosing which connection to use. You could use either WIFI only or both WIFI and Mobile connection. However as the amount of data downloaded at anyone time is minimal, it wouldn't be too heavy on your data plan. Do monitor data usage to see whether or not it suites your need.
The user is free to choose the ring tone for each account entry, allowing you to identify the problematic server without having to look at the phone logs. Internet connectivity is also monitored and the lack thereof will be notified to the user at the previously set time interval.
Each of the servers is checked in sequence, but should an error occur on at least one of the accounts, the monitoring interval is changed to 1 min. Should it not correct itself within 3 attempts, a notification will be shown and the previously set ringtone sounded.
The application doesn't cause much trouble on the battery life or memory of the device as it isn't constantly running. The monitoring is scheduled using the AlarmManager allowing the app to dispose all the resources. It wakes up during the interval, checks the servers and disappears completely.
I have not been able to do much testing on various phones, but it has been extensively tested on the HTC One X and the HTC Desire (bravo). Constructive criticism is welcome and should you encounter a problem with the application, please drop me a line so that I can improve the application.
HTC users with Sense 4+, will have a problem with the smartsync, which knocks off all internet connections (Wifi and Mobile Data) between 00:00 and 07:00 (unless the phone is connected to the charger). Please take note that the application will mark this as a network error.