Hi,
You could take a look at the Sketch Graphics Layer (and its reference documentation).
For text, you would probably want to look at AGSTextSymbol, AGSGraphic, and AGSPoint.
See also this Sketch Layer Sample on GitHub.
And although this sample is for the OS X SDK, the principles are much the same. That page also includes a link to this download page for the Samples app (look in the app under "Building Maps --> Sketch Layer").
Hope that gives you some answers.
Cheers,
Nick.