There is a separate listing for Android apps! I have an Android phone so I don't normally look at iPhone apps, but this one looked interesting. It's also available as a regular web page:
http://www.frictioncalculator.com/
Single-point friction values in dry conditions and without any qualification of roughness, temperature or pressure, and excluding wear and durability characteristics, are a mere speck in the knowledge base of any tribologist, but it must be progress to have this data so easily available in the field. It's also interesting to think what may be possible in future with mobile design/analysis tools; this was the idea behind starting these lists of apps.
If you have found any other interesting iPhone apps for tribology, why not add them as replies to this post?