Are products like redguard fit for use as a waterproofing membrane for shower pans or floor applications?
Redguard (tech sheet) passes the ANSI A118.10 and A118.12, which include waterproofing

Shower pans are a critical assembly and have to be treated as a system.  Both Schluter (sheet membrane Kerdi) and Laticrete (liquid membrane Hydroban) use a wide flange drain assembly that improves the transition area between membrane and drain.