Does this sort of consulting service exist? Does it have a name?

A friend of mine is leading the "search" process for a major technology overhaul at his company. Basically, they are a large enterprise and are going out to seek bids as they look to modernize their website, CMS, mobile apps, etc.

My understanding is that they are going to a number of specialized and more general tech consultancies and dev shops, and are gathering bids through a "scoping process" with each firm.

While I would love to help act as a more informed advocate that could guide them through the process, I have neither the time nor the deep experience required to offer the best possible advice.

Is there a service out there where a client can hire an independent consultant to serve as their liaison and advocate through the search process? This person would not be tasked to perform the project; rather, they would help the client ask the right questions, advise them through major decisions, help de-construct proposals, etc.

If so, does this sort of service have a name?