Indeed! HATop is great to show the status, traffic, HTTP codes, errors or number of connections. It is also very simple to enable/disable HAProxy backends, for example:

  hatop -s /var/run/haproxy/example.sock

Use the arrows to select a backend server and press:

   F9 - Enable a backend server (Status: UP)
  F10 - Disable a backend server (Status: MAINTENANCE)

For Apple keyboards it is fn+F9 and fn+F10.