Can I input a video signal into my HTC phone to use it as an external monitor of a camera?
If your HTC phone has OTG support. You can use one of these USB OTG adapters. Then you can plug your 70D using a mini USB cable and then plug it in to the OTG cable and plug it into your phone. Then you can download an app such as DSLR Controller and you should see  live feed of your 70D on the phone.