Although the Alexa Android app may have intents, there probably won't be any intents which allow control of the Echo itself (as most of the features are controlled by voice).
I have been considering another way of doing this, by creating a custom app which uses the Alexa Voice Services but takes the audio input from another source (such as text to speech) instead of from user input. This app could stream the audio from Alexa over Bluetooth to the Echo or Echo Dot and would give the impression that the speech is coming from and not from the app.
This could then work a bit like hack which involves disassembling the voice remote and connecting it to a Raspberry Pi, but less destructive.