After buying an Apogee Jam and putting it through the paces with the most popular guitar modeling apps for iOS I settled on Positive Grid's JamUp XT Pro as my favorite. So I bought their JamUp Plug. Figured why not at $20.
Certainly gets the job done and at $20 with a smaller footprint than the Apogee Jam I believe this will have a permanent spot in my travel bag.
If you are looking for a cheaper interface the JamUp Plug can't be beat and I think most people would agree that their JamUp XT software is really turning heads. It is also 50% off, $10 instead of $20, right now as they are having a NAMM sale.
Here are a few pictures.