You should definitely get ARUP Consult. It's like the Lab version of epocrates. Instead of drug info it gives you authoritative lab info - from algorithms to concise diagnostic advice. Look up a disease and it'll let you know the tests that could be run for that diagnosis and its specifications. It's a must for any health care provider and available on any platform.
Web:
http://www.arupconsult.com
Mobile:
http://m.arupconsult.com