If you're looking for something simple and out of the box for ArcCatalog, you can simply make a GIS Server connection to your ArcGIS Server machine with a publisher or administrator type connection and start and easily stop services; no need for Python or an extra toolbox (although those tools are great).
ArcGIS Help 10.1 - Connecting to GIS servers
If you do find you want something to put into a Python script, Kevin Hibma published some nice Python snippets on GitHub for administering ArcGIS Server.
khibma/AdministeringArcGISServerwithPython_DS2014 · GitHub
