Timer / timing question

Unity Engine
1

This only took me about a few weeks to come up with in spare time:
http://screencast.com/t/7DUKtU03EO

However, what I really want to do is a circle / pie thing that uncovers and keeps around the edges of the “gem” square, any hints on the best approach to this problem?

2

There’s a suggestion in this thread about using a cutout shader to reveal a non-linear gauge.