Yeah I was stupid and bought an iRig last year (for a lot more).
Not worth it even for 16.99 imo. Noisy, and low volume. See complaints in IK's forum.
The iRig uses the iPad/iPhone analog mic/earphone jack and less than stellar AD/DA. But IK have updated their excellent Amplitude app to now support digital connection via the dock (which Garage Band and most other audio apps already did), so it's no longer necessary to use an iRig or other analog interface. Dunno if Line 6 still require use of their interfaces for their apps, never bothered for that reason.
There are better interfaces available (although at higher cost) for either analog or digital connection, such as those from Tascam which also include a mic pre with phantom power and even MIDI (only available as separate i devices from IK).
IK's software I like very much, but their hardware, not so much.