Full Phoenix sun, and you don't want to have to do much maintenance, but you want to shape, and you want it to be about 2 feet high ...

Santolina ) comes in a grey-green (http://www.desert-tropicals.com/Plants/Asteraceae/Santolina_chamae.html and dark green species http://www.mountainvalleygrowers.com/sanvirens.htm

And it's naturally a short plant that takes to shearing better than most.

I love the sound of lazy's santolina hedge suggestion, and wouldn't it smell GREAT when you trimmed it??! Love it. Upright rosemary would also work out too, although it does tend to get pretty darn woody when it's older so that after a trim it's a bit stumpy looking, but bounces back eventually.

Another plant that I've seen grown in tall or short sheared hedges is good old true myrtle, Myrtus communis. It wants to grow taller than two feet but if you keep it trimmed it will abide by your wishes. I put a link to it on Desert Tropicals below. They say no water but I feel it needs occasional irrigation to be happy.

Let us know what you try and how it works out.
Take care,
Grant

Here is a link that might be useful: True myrtle