The http profile itself should not interrupt traffic, though its application will cause the VS to drop any traffic that is improperly formatted HTTP (or which is not HTTP at all). It should also not cause any traffic drops at the moment it is applied.
In any case, I admit that you follow-on question is somewhat unclear to me. When you write "... how about for the application that I want to monitor", do you mean that you want to log something from a BIG-IP monitor used to health check a pool member/node? Or do am I misreading your request?