I recently saw an announcement for Interview Assistant Pro HD for the iPad (http://mobile.intersog.com/07/07/interview-assistant-hd/). I spent the $3.99 (current price as of October 22, 2011) to look at it.
BLUF: Don't bother (overall).
Interview Assistant Pro HD (IAPHD) can be useful for organizing your own questions, but the MT Interview Creation Tool will give you much better questions and make you think carefully about what's really important for the position. Few of the questions I found in IAPHD were behavior-based. For example, one of their IT Project Manager questions is "How do you identify and manage risks in your project?". IMO, a much better question would be "Give me an example of where you identified and mitigated risks in one of your projects." Many of the questions I saw were rather philosophical or knowledge-based.
There are times (in my view) where technical questions are important. For a recent IT position, I asked the candidates "Describe for me what a SQL Injection attack is and what steps an application developer can take to mitigate the likelihood of such an attack". I had specific evaluation criteria for that question, including ones around how well the candidates could communicate the answer to a very technical question. Many of the questions I saw in IAPHD were of that sort of technical base.
As another point of comparison, the MT Interview Creation tool provides criteria to look for in an answer. IAPHD does not, nor does it (easily) provide a means for you to put that into the question.
As a final point, I didn't find any way to print a set of questions. I think they are assuming you'll somehow type the answers in on the iPad, which I would not consider good practice. While I am a techno-nerd, I do agree with MT that recording answers on paper during an interview is orders of magnitude best practice. A dozen sheets of paper with my questions (and room for answers) and two pens is not going to suffer a technology failure in an interview. And the paper approach lets me focus on the candidate, rather than on my technology.