Like @rocketwiz described, Tasker would be one option, MacroDroid may be another. You may be able to initiate the app directly on the device, but I'm not 100% sure of how to do it, if it is possible.
There may be local options with Tasker and one or two of it's plugins, but the one I would feel most comfortable guiding you through would be something like:
- Install and configure Tasker and AutoRemote plugin (there's a few steps to go through with this part, hopefully you can find enough online)
- Make sure your phone / device has a fixed IP on your local network
- Create a Virtual Button device on HE
- Add the button device to the dashboard, including setting up a tile
- Create a rule, e.g. RM Rule, triggered by the pressing of the button
- For the actions in the rule, make a HTTP GET call to your phone, with something like:
http://< Phone IP >:1817/?message=NetFlix- Replace the
< Phone IP >with the IP Address of your phone andNetFlixwith whatever text you like at this stage
I might need to come back with part two of these instructions.... 
Maybe later this evening or tomorrow. But if you are proficient in Tasker, you want to create a profile triggered by an event from a plugin, being AutoRemote, filtering on a message with the text you put in place of NetFlix above. Then add an action to open an app of your choosing. Don't worry, I can guide you through this part later if needed, or someone else...
I'm also working on a Tasker integration to make some of this stuff a little easier, so this post gave me some ideas or at least inspiration to include something like this. I just haven't added it to the list yet...