About four years ago I was looking around for ways to solve the same problem in the context of a build system. In the end I settled on a hand rolled database based solution because I couldn't anything that fit well in CPAN. Over the four years since the system was turned on its processed about 800,000 tasks and now runs around a dozen "task clients" on Windows XP, Vista and Windows 7 (32 and 64 bit), various versions of Debian and a couple of Mac OS-X versions. The database based design has been very successful!

The original design relied on a server that handled email used to manage tasks, but there is now a web UI for the system so the only thing the server really does is provide the database. I find having task history recorded in a database is a great tool for diagnosing issues with the system and tracking the evolution of tasks and the system over time.