Good question, I love both of this tools, while IFTTT is more about automation, on Hooks we are focusing on notifications only. Our value is the content, it's very easy to create alerts about many things with just one click.

Actually we are working on adding Hooks as an IFTTT channel later this month as a trigger so anyone can build their own receipts.

How does this differ from Pushbullet's channels?

I came here to ask the same thing, sort of. Pushover and Pushbullet both work with IFTTT, and IIRC used to be the only way to get IFTTT to send you mobile push notifications.

However, now that IFTTT supports push notifications, why do you still need Pushover or Pushbullet?

This is the first I've heard of Pushbullet, and boy is their marketing frustrating. I just spent 5 minutes trying to answer the question "Is this a service which turns an HTTP POST into an iOS push notification?", only to be greeted with answers like "Bring together your devices, friends, and the things you care about". Argh.

In that case you'll like Pushover's home page: https://pushover.net/

There's a sample curl command right there on the page.

EDIT: Pushbullet's home page has a link to API docs, and it took 30 seconds to find this: https://docs.pushbullet.com/#create-push

+1 for Pushover. I'd been using Slack for device notifications, but Pushover is much faster. I've had both running simultaneously and the Slack alerts would sometimes arrive minutes after Pushover.

You might also want to check out Boxcar.