See http://www.arrl.org/ares-el?issue=2013-03-20 for details.
To search for iPhone or Android apps, use keyword "MGRS".
I guess that US Amateur Radio operators may be well advised to migrate away from Maidenhead LOC and switch to USNG.
Kudos to Al, KF4KIR for pointing to this information and for immediately getting back to me with additional information!
Due to this new information, RaDAR-America Contest rules will be amended momentarily to the effect that USNG coordinates will be preferred for the logs of US HAMs.
73 de Marcus KD0JKM