Pogo Connect
Pogo Manager SDK
Add pen pressure and palm rejection to your app.
It's free, and has simple integration with Xcode.

Pogo Connect is a best-selling pressure-sensitive pen for iPad. By adding support, you enable thousands of users to interact more intuitively with your app.

Shoot us a note, and we'll send you a brand new Pogo Connect for testing. For reals.
libT1PogoManager
Download the SDK (v1.3.3 Jan. 20, 2014)
For instructions, see T1PogoManager.h.
[SDK] | Release notes | Release history
libT1Store
Download a sample project
See how easy integrating the Pogo Connect is, as well as the configuration options.
[Download]
libT1Store
Try it live on the App Store
Procreate did a fantastic job integrating Pogo Connect.
iTunes Link