Yeah my best friend is that way, absolutely unreachable by phone even though he keeps it on him at all times. He tells me "any time you need anything or there's an emergency I'm there" but the few times anything really important has come up he's terribly unreliable to reach. I'll send a message to him and he may reply 3 days later?

It's at a point where I've given up considering him an emergency contact, even as he claims he wants to be. I hope you never get burned by your "I can't be reached unless I decide I'm in the mood to reply" policy.