I just wanted to know if anyone else is getting the same problem as me, I'm running the companion app on my nexus 5 (2013) and the battery seems to be draining at an alarming pace when it is running, and it also makes me phone hot. Is it just that my phone is just too old to run it or is there another reason why it does this?

Its draining the battery because it has a constant Wifi communication link with your PC. Its normal for a phone to get hot when used like this.

I use my phone as a GPS and that drains the battery like nothing else. I need to plug it in or the battery will be drained in a few hours.

Cell phone aren't made to be active constantly. Battery life is only good when they are inactive 90% of the time.

Couldnt have said it better myself.

If you want to use the app, best to keep your phone plugged in. I only use it on smoke breaks to fiddle about with my inventory.

but I've used other apps on my phone that use Wifi extensively but i haven't used an app that drains battery so quick as this one does. I don't get a few hours from it, i literally get an hour's worth of use out of the app from full charge before i get the 5% battery warning. What is it doing that it's eating through my phone's battery that quick?

Well I'm sure the app could be better optimized. It could use a lot of CPU and RAM resources as well. I wouldn't worry about it, just plug it in, when using the app.