We would be more than happy to see someone port Pagerbot to use Hubot instead, though.
I had PD set up to attempt contacting me four or five times in a half hour by SMS and phone until I learned the service better. It also supports Android Push which seems to get delivered faster and also I believe has no incremental cost at PagerDuty. Now I also have a tablet that's usually in WiFi, so I get android push before the SMS goes out, and only need to get SMS when my tablet is out of WiFi range.
You're paying for the reliability, the integrations, and the excellent support staff. Just read the PD blog. They are obviously "top men" working at PD. We pay other services a good bit more per-annum and we usually see them going down all the time. PagerDuty pretty much stays up, and it works with everything.
We do in fact have top men and women on our eng team if anyone is looking to join http://pduty.me/1DEFTuV
I'm on the sales team here at PagerDuty. Feel free to send me a note at mark at pagerduty dot com and we can work something out for your team regardless of size.