Added my prompt theme, with a tweak to the core oh-my-zsh to support it. My git_prompt_info function not only reports the branch and dirty status, but also whether or not the branch is ahead or behind of the remote, or both. It also switches the prompt colour from green to red if the previous command exited with a non-zero value (i.e. failed).

lib/termsupport.zsh

@@ -4,6 +4,7 @@ case "$TERM" in
       print -Pn "\e]0;%n@%m: $1\a"  # xterm
     }
     precmd () {
+      oh_my_zsh_theme_precmd
       print -Pn "\e]0;%n@%m: %~\a"  # xterm
     }
     ;;
@@ -14,6 +15,7 @@ case "$TERM" in
       print -Pn "\e]0;%n@%m: $1\a"  # xterm
     }
     precmd () {
+      oh_my_zsh_theme_precmd
       echo -ne "\ekzsh\e\\"
       print -Pn "\e]0;%n@%m: %~\a"  # xterm
     }

themes/lazyatom.zsh-theme

@@ -0,0 +1,40 @@
+git_prompt_info() {
+  branch=$(git symbolic-ref HEAD 2> /dev/null) || return
+  git_status="$(git status 2> /dev/null)"
+  state=""
+  case $git_status in
+    *Changed\ but\ not\ updated*)
+      state="%{$fg[red]%}⚡"
+    ;;;
+    *Untracked\ files*)
+      state="%{$fg[red]%}⚡"
+    ;;;
+  esac
+  
+  remote=""
+  case $git_status in
+    *Your\ branch\ is\ ahead*)
+      remote="%{$fg[yellow]%}↑"
+    ;;;
+    
+    *Your\ branch\ is\ behind*)
+      remote="%{$fg[yellow]%}↓"
+    ;;;
+    
+    "Your branch and")
+      remote="%{$fg[yellow]%}"
+    ;;;
+  esac
+  echo " %{$fg[yellow]%}(${branch#refs/heads/})${remote}${state}"
+}
+
+function oh_my_zsh_theme_precmd() {
+  local previous_return_value=$?;
+  prompt="%{$fg[light_gray]%}%c%{$fg[yellow]%}$(git_prompt_info)%{$fg[white]%}"
+  if test $previous_return_value -eq 0
+  then
+    export PROMPT="%{$fg[green]%}➜  %{$fg[white]%}${prompt}%{$fg[green]%} $%{$fg[white]%} "
+  else
+    export PROMPT="%{$fg[red]%}➜  %{$fg[white]%}${prompt}%{$fg[red]%} $%{$fg[white]%} "
+  fi
+}