[scarface74]

A third party code escrow account with instructions on how to build the service and a contract that specifies conditions when a customer gets access to that escrow.

I've been on both the customer and service end of such agreements.

[nielsole]

Is there a popular provider for doing this? It sounds like a lot of work to find a solution in which both parties trust (both technically versed and reliability wise). A common notary probably wouldn't cut it, right?

[scarface74]

Both companies I’ve worked for - as a client and a customer - used Iron Mountain.

http://www.ironmountain.com/information-management/software-...

[detaro]

There's a bunch of companies doing it, some dedicated, some as part of larger related offerings. E.g. I know NCC Group (large IT security company) does offer it, TÜV (which does all kinds of certification and compliance work), ...