I just uploaded a small tkinter python script I made for i3wm. The script is very minimal and provides a small interface to shutdown/logout/reboot (might add suspend/hibernate).
Here is a screenshot of how it looks on my current config.
The script is available for download at github.
To get the floating window you need to add the following to your i3 config.
for_window [class="Tk" title="tk_logout"] floating enable, border 1pixel
If anyone has any suggestions or feedback, please leave a comment.