You should check out Parse (www.parse.com). You can both send push notifications and write server side scripts using JavaScript using what they call Cloud Code. It's pretty awesome.
Parse is cool, but the pricing is a deal breaker for me. According to their plans page (https://www.parse.com/plans), I'd need a pro account to enable multi-app push. Pay Pad is three apps actually so the combination of UrbanAirship and Webscript.io end up being a very cheap solution if I wanted to ditch my current implementation on Heroku.
Although I suppose you could get around the multi-push-certificate restriction with multiple Parse accounts. If you had two iOS apps, then you'd be making two web requests out to Parse. Although I do this now with UrbanAirship so there would not really be a difference. Interesting.
Possible alternative may be https://script.google.com -> "Script as Web App"
Especially when integrating with google's apps for domains and APIs.