The Tri-Partite Agreement
This agreement, proposed by Rabbi Michael Broyde, anticipates extreme cases, such as if the get refuser cannot be found. It uses a formula of three different halakhic principles (hence, tri-partite) to create an agreement to be signed during the wedding, once after the kiddushin is performed, and once again after yihud.
The proposed text can be found here: Tri-Partite Agreement
The underlying halakhic principles are set forth in this article by Rabbi Michael Broyde: A Proposed Tripartite Agreement to Solve Some Agunah Problems: A Solution Without Any Innovation