No, it's not creepy, just good business. Learn what your customers are purchasing, offer them incentives for being a loyal consumer, and communicate those benefits with them directly to their mobile device.
Learn the spending habits of your consumers and keep track of their payments. Offer discount campaigns and loyalty rewards that will keep them coming back for more!
Consumer communication is key for any business. Keep unlimited, detailed log notes on each of your customers and schedule follow-up communication that ties directly to your calendar to serve as a reminder.