Here is a problem that I would pay a subscription for a great solution to: Cron as a service.

Sometimes when you set up a simple codestack on Heroku or Parse or similar, it would be great to be able to specify a web hook that should be called repeatedly just to run maintenance code, summarize scores, clean up logs etc. If you have root access you can set up cron but this is not always the case, and I think it would be possible to build a SaaS that people feel is easier to use and more flexible than cron. I would easily pay a few dollars a month for a simple reliable cron service. Reliability is key, your service needs to never ever fail.