iPad as external monitor for Logic/PT?

Not exactly a second screen, but check out an app called TouchOSC. It is great way to put your mixing / playback controls on your ipad screen. I love it.

 

Yes, Avatron AirDisplay:

https://itunes.apple.com/us/app/air-display/id368158927?mt=8

I've used it with Logic before and is great app for making your iOS device a second screen. Although like any wi-fi connected device, latency issues must be considered and since working with audio needs some critical timing, certain uses could be an issue. Sometimes I've used it to keep a virtual instrument in view on my iPad, so I can tweak the settings there and not have it get in the way of my arrangement window on my Mac's screen. I would say check it out still. It has some fun and practical uses even outside of Logic.

Or as rockstarjoe mentioned, go with TouchOSC if you want your iPad to be a dedicated mixer controller to Logic. I also just bought Lemur for iOS, but I haven't played with it yet, but it's a top class wi-fi controller app for your DAW.

 

Controllers such as TouchOSC and V-Control etc are good. I've tried AirDisplay and others for extending the screen and it was quite laggy. In saying that, I tried it on an iPad2 so on an iPad5 ymmv.