Gaydar Shopping Help!

I was browsing radioshack.com the other day and I noticed that a bunch of companies have started coming out with gaydars devices. I was wondering if any of you had experiences with these and could tell me which one to buy.

Here are some of my questions:

Should I look for a gaydar that will tell me whether someone is bi or gay or just one that will tell me if they're interested in members of the same sex?

Should I look for one of the stealth models? Which is better the wristwatch gaydar or the sunglasses version?

Which gaydar has the highest rate of correctly identified gay men?

If I buy a microsoft gaydar will I be able to use it with my mac computer to download new gaydar apps?

Could someone with a strong interest in musical theatre or who is wearing particularly tight pants trigger a false positive on my gaydar?

Does the iPhone gaydar app actually work? Is it worth buying an iPhone?

I've never bought one of these before. I'm really excited. I just want a little advice before I make my investment...