Norris Vivatrat, MD, an affiliated clinical instrutor at Stanford, and Chris Marcellino recently released a free iOS app that is designed to help medical students and residents calculate opioid dosage conversion for pain control. According to the authors:
The application supports conversion to and from opioids commonly prescribed and used in U.S. hospitals orally, parenterally, or transdermally, including morphine, codeine, hydromorphone, hydrocodone, fentanyl, methadone and oxycodone.
I did not test the application for accuracy, so I can't comment on the reliability of the calculations. The interface, however, appears to be straightforward and relatively easy to use. Opioids Dosage Conversion, which also includes a reference chart, runs on both iPhone and iPad.