What is Open AT?

Open AT is a Wavecom product. The following is from Wavecom website:

Open AT® is the worlds leading embedded cellular development environment. In a nutshell, it allows creative developers to write applications in standard ANSI C and natively execute them on Wavecom Wireless CPUs, and reduce cost in the process.

Open AT allows you to embed your control program (which issues AT commands) inside the Wavecom product.