It worked, but not quite the way I expected. The chia died over the winter, but the dead chia continued to hold the soil in place for 2 more years. The perennial seeds I had mixed in with the chia didn't take hold, but the stuff that was growing naturally both above and below the eroded spot, used the chia as a bridge and colonized it. I now have clovers and wild carrots holding my hillside in place :)
Thanks, my question now is where did you get the chia seed?