Ask HN: What are good alternatives to PagerDuty?

Although generally happy with their service, I'm getting absolutely frustrated with their sales team. We did a trial with their "Event Intelligence" add-on, and it solved a pretty big issue for us. Problem is now getting someone from sales to reply to our e-mails. Been trying to get in touch for a weeks now, but I'm yet to get a hold of someone. I'm now fed up, and I'll rather spend my time migrating away than wasting another second trying to get someone to take our money.

Long story short, what are good alternatives to PagerDuty?