The iReformed Reference Library is a very handy iPhone app.
As you can see below, it contains Christian creeds, along with Presbyterian and Reformed confessions and catechisms.
The Westminster Confession used has the modifications that are found in US versions.
When the Shorter Catechism is opened, firstly only the question shows.
The answer and Bible references appear when you press ‘answer’. Roaming catechesis!
All in all, worth $1.20.
HT: The Ruling Elder. (Who provides a more detailed review.)
mgpcpastor's blog 