Seems weak, only protects through the Grand Jury phase, and lawyers are not allowed to accompany you in the Grand Jury testimony phase - they wait in the hall like everyone else.
On the other hand, a good lawyer up to that point may save you from further action.
Cost is buried in the website - $130 for 1 year, $400 for 4 years.
I'm personally shrugging, can't see a huge need for it. After Tuesday, on the other hand . . . . . (he gets to appoint the big shot Fed lawyer prosectors)