The key to accountability is visibility of expectations and results. Stated commitments tend to be heard differently by different people, and remembered differently over time. Systems of clearly posted commitments, with names and dates, are easier to track and control.
We have guided the implementation of many different visual systems of ensuring accountability, and have found that the critical elements were that they be designed by the group that will use them, and that they are visual. Being visual means they are almost always posted on a wall, rather than in someone's logbook. They are best kept simple, with the use of colors, positions, etc. In most cases the system can be tied to Standard Work.