One niche that has really taken off in the text alert industry are stock trading companies. Customers of these stock trading customers are prepared to spend hundreds of dollars (if not thousands) to simply receive updates on their stocks, or receive other stock trading tips. These have been traditionally sent via email, but they can more reliably, and more quickly be sent now via text alerts.
Your customers can subscribe by either texting your keyword (which is generated for you when you sign up) into the system, or by visiting your signup page that is also generated for you. If you already have a large list of numbers, you can import those via an Excel spreadsheet.
After your customers are in the system, you can either send out messages manually (organizing different numbers into different groups to send out specific messages only to specific people) or if you a real ambitious, you can integrate your stock trading software with our message sending API to automatically send messages out at different times.