Arduino -> Android -> web, how?

Question

Android

I'm making a standalone parrot feeder. Meaning: if I am not at home for several days, I send a command and feed is poured on him.
I have:
1) arduino + hc05
2) old phone on android (4.2.1) + apartment wifi
Idea: send commands via the Internet to an old phone that would give a command to arduino via bluetooth / usb. What is the best way to organize this?
Ready-made applications for controlling arduino - do not allow you to do this remotely. It is necessary, probably, as in the IFTTT application - sent a letter with the text "1", such and such a command was executed, and so on.

Answer 1

The idea is interesting, but using the phone as a proxy for such an undertaking as shooting an ant with a shotgun, it would be easier to use ESP instead of it and hc05 . Moreover, in this scenario, the arduin will not be needed, because ESP can also pull 1 relay.
If we still take "what is" as a basis, then 2 problems arise:
1. NAT, because the phone goes to the Internet through the apartment's WiFi, which means that IP does not smell like white here, therefore a direct connection to the phone from the outside will be impossible in principle.
2. Mechanics, given that the feeder is on the street with constant changes in temperature and humidity, it will not be easy to make it reliable.
Solution 1 problem:the smart should have an application that will "wait" for commands, tk. you can’t send anything directly to it; it’s easier to use push services, since there are mountains of examples, in total, the application connects to the push server and waits for notifications from it when it receives a connection to the bluetooth and sends it a command (serial protocol). There are no special problems here, you need to be able to google and know a little java or C #, as you did something similar, it took no more than an hour to google.
Solution 2 problem:here I would advise you to google analogues and read what pitfalls their creators faced, so as not to repeat their mistakes. There are many options for iron, but the essence is 1, it will be a relay or a pair of relays (you can buy a ready-made module), a power adapter (probably not weak, because the engine can create large currents) an engine or a servo or something like that (there are many options), capacitors for smoothing currents from motors, diodes, and ideally, I would hang a stabilizer / current limiter (a simple circuit with 3-5 parts), because the engine (if it jams) can consume currents in amperes, which not all power adapters can withstand (can catch fire in the worst case or arrange a short circuit). Plus, there must be a fuse so that in the event of a short circuit, a fire does not occur (given the remote nature, you probably will not have time to extinguish it).