Redirect scripts

If I got a microsite ranked really high in Google could I run a straight redirect to my main site?

I was thinking about putting a redirect inside an iframe on the page, and only showing the iframe if the user agent isn't a bot, as I've heard Google doesn't read iframes... Is this true?

Or if not whats the best way to go about it?

first, google reads iframes - so dont count on that
secondly, redirecting based on useragent only will probably trigger a ban extremely fast since useragents strings are simple to customize and fake.
if you want to differentiate a real user from Google bot / manual reviewer, you'll need more than just useragents string, such as:

1. bots ip's and net ranges - you need to collect lots of data
2. cookies
3. referrers
4. dynamic url parameters
5. geo ip's detection
and many more