You can use curbi to block server-based apps only.  Offline apps are not able to be blocked on iOS.  

All you need to do is add the URL's for the App into a rule.  Here's an example showing you how to block Netflix using an Adhoc rule from Safari.

To set up a rule, log into your curbi account, click on the device name, then click on the "Rules" tab and then click "New Rule"

Then select the type of rule you wish to use:

Bedtime, Study Time and School Time rules are preconfigured for School Days and weekends, a Flexi and Adhoc rule allow you to determine when to activate the rule.

In this example, I chose an Permanent rule it allows me to block the App Indefinitely.

After clicking on "Permanent" then click on "Add site"

This is where you add the URL's for the App you wish to block.  Some Apps have more than one URL.  So if your not sure, just email in and we can tell you what to use.

Netflix has 4 URL's required to block it, so you add each one separately as shown.

Then click "Next"

Set the required time you wish to block for, and click "Next"

Select which device you wish to apply the rule to, and click "Next"

Name the rule and decide here if you wish to save the rule for later use.  i.e. If you wish to apply it to another device at a later stage, you don't have to redo the rule.

Then click "Apply Rule".  The rule will Activate immediately if set to, if not I will sit in the Inactive Rules until its time to switch on.

That's it!