Design your curriculum with attention to the theory and history of drama. Include readings from the early Greek theater and readings on the theory of pathos and catharsis. Create assessment material to evaluate your students' understanding of the foundational elements of theater. Assess your students often to help drive your instruction.
Compile writings on technique---since you will not be in person to deliver lectures explaining the theoretical basis for this art form, it's important to give substantial reading material.
Set up a discussion thread that supports the collaborative exploration of the theoretical elements of theater. A platform like "Blackboard" or "WebCT" can support this kind of technological element. Require students to interact with the material and each other through this means---this will allow you to assess both their understanding of theory and whether of not they did the work. Emphasize the theoretical component of drama and theater---drama takes place in the mind before students successfully execute it on the stage.
Pair theoretical writings and assessment of student understanding with active assignments. Require students to have a webcam for the course (many computers come with them, and external webcams are decreasing in price). Assign acting tasks to students based on the reading of theory.
Model acting technique through your own videos. Upload videos often---it is important for student to have a model from which to work and by which to judge themselves. Provide feedback to student work in both writing and video.