Well, I know it should be published before, as I felt BuddyPress really should have this feature. I like  to have unlimited nested conditional fields in my BuddyPress site registration and profiles. As example,
You want Car details of your user, So, your fields should be

1. Do you have a car? ( radio button/dropdown selectbox )

1a. Yes

2. Which Brand?

2a. Audi

3. Which Model of Audi?

3a. Audi A4

3b. Audi A5

3c. Audi A6

2b. BMW

4. Which Model of BMW

4a. BMW ActiveHybrid 3

4b. BMW ActiveHybrid 5

4c. BMW ActiveHybrid 7

2c. Cadillac

1b. No

5. Do you want to buy a car?

5a. Yes

6. Your Budget?

7. Brand?

5b. No

I guess you understand now what I going to do. this kind of things is not possible with BuddyPress now. The new plugin is just to do that.

Any suggestion is welcome. Going to release it in next week! It will be a paid plugin.