Odyssey does have the notion of callback's. Its goal is perseverance across bandwidth change. Transcend is under the control of user. A user sets parameters which indicate desired Fidelity. Odyssey is a resource management tool with a single user interface.
Agility is a measure which concerns the ability to adapt to varying situations.
At the two adaptation extremes are Laissez-faire and application transparent . In the first case the application is completely responsible for adaptation and in the ladder the system is completely responsible for adaptation. In the middle is application aware adaptation. Here both application and system work together to adapt. Eudora is an example of application adaptation.