When bash is called non-interactively, PS1 is unset. However, if it's a login shell, ~/.bash_profile is still sourced. Therefore, testing PS1 tells us if this is a login but non-interactive shell (such as: ssh host 'uptime'). Testing PS1 before setting it preserves that state for later tests if desired.

vbell off
bell_msg "^GBell in window %n"
defnonblock 5
nethack on
hardstatus string "%{.bW}%-Lw%{.rW}%50L>%n%f* %t%?%{.cW}(%u)%{-}%?%{-}%+Lw%L< %-20=%{..G} %H%-8= %{..Y} %c " 
hardstatus alwayslastline
activity "^GActivity in window %n"