Contextview shows contexts in alphabetical order and sorted by priority. This allows a nice view of contexts and todo items within each as well as those not in a context. It takes an option to grep across the todo.txt file so can be used to find by context or free form text etc.
Usage: todo.sh contextview testing
Contextrename allows you to rename contexts across all the todo.txt file or just one or more lines.
Usage: todo.sh contextrename oldcontext newcontext 1 3