Text Count Alert is a very simple application designed to keep a tally of your outgoing text messages to prevent incurring additional charges. However, it has plenty of customisation included.
I can't speak for other countries, but here in the UK most folk have a certain SMS allowance whether on a contract or using pay-as-you-go. The problem is that once the allowance has been used up your network provider will then bill you for any additional messages.
That's where Text Count Alert comes in handy because as well as just keeping track of how many messages you have sent there are a whole host of notification alerts that can be set up - such as when you exceed your limit or alert once at a certain count. These numbers can all be customised so you can give yourself a warning when you are close to your limit. You can even set the app to prevent you sending text messages once you get to your allowance - clever stuff.
For $0.99 Text Count Alert is a bargain if you ask me - especially for teenagers who may be relying on mum or dad paying the phone bill each month. A great application.