Simply Hax are plain cheating/utility modifications, which, unlike pretty much all other cheat mods, should not interfere with notch classes. Thus, they should be compatible with anything that isn't another cheat mod doing the same thing.
Simply Hax Flying:
By default press "R" to start flying, ascend with SPACE, descend with LCONTROL. Also allows you to run faster by holding LSHIFT.
Key bindings and max flight speed can be configured in auto-created file under /mods/SimplyHaxFlying.txt
Works in SMP with the usual restrictions.
Simply Hax Vision:
By default press "I" to make close walls disappear from your sight. Extremely useful for finding cave systems!
Key bindings and disappear range can be configured in auto-created file under /mods/SimplyHaxVision.txt
For more info go to the forum of minecraft: http://www.minecraftforum.net/topic/541676-