Would be awesome if you could trigger VisualCron to start a job from an external trigger. What I would do is embed a super-simple, small HTTP and/or SSH server that could be setup to run on a user-defined port.
VisualCron would tie then expose a URL that would trigger a job when the URL is hit. For example, I could configure an HTTP URL such as
http://my.domain.com:8080/trigger/job1 , to trigger Job1 on VisualCron.
Bonus points: Allow HTTP URLs to which one can GET/POST to send data (primarily JSON, XML or FormData) into the job, to be used by the job.
That would be powerful and a minimal security risk.