Can I Open an External App within the Agnitio App?

A: Yes. 

To open external URL use the schemes "agnitiodefaultbrowser" and "agnitiodefaultbrowsers" instead of http and https. iPlanner will intercept these and forward them on to the default browser on the iPad (i,e Safari)

e.g.

agnitiodefaultbrowser://www.apple.com

agnitiodefaultbrowsers://www.apple.com

To call another app, you need to know its URL scheme. There are some default schemes for built in apps on the iPad. For 3rd party apps, you need to know their schemes:

Apple-Apps info:

http://developer.apple.com/library/ios/#featuredarticles/iPhoneURLScheme_Reference/Introduction/Introduction.html#//apple_ref/doc/uid/TP40007899