Avnish,
The concepts behind the PMP are more-or-less applicable to all projects. The individual methods - broken into two camps, Agile and Waterfall - incorporate all the concepts however they are executed differently.
I have said it before on the boards: I am not, per se, a "project manager" in that I don't do that as a profession. However, as a consultant, I must manage projects professionally. From that perspective, that is where I have found the highest value of the PMP certification. Studying for the PMP exam opened my eyes on how to better serve my clients in the projects that I execute for them.
So, I think it's very relevant, regardless of the method of project management used.
My 2-cents.
Harry