Here's the idea -- there's a website that I want to scrape. It updates every 10 minutes, but sometimes get's out of sync. It's important that the information I scrape is just before it updates. Each time I check the site, I can scrape the 'time remaining' until next update.  
Is there a way to make a cron job that -- after each iteration -- I can specifically set the time to wait before running the the time (t+1) iteration based on some variable from the time (t) iteration? 
I'm not particularly familiar with cron jobs -- my current super rough implementation just uses -sleep-. Not ideal.
You could use the 'at' command to set a new job for the next time you need to run it. 
So if your scraper tells you the next update is in 7 minutes you can set the 'at' command to run 'now + 6 minutes'
Variable time between cron jobs (or similar implementation)