Arduoino Mega with multiple sensors...

Need some ideas...

how to attach multiple sensors with arduino mega.
I want to attach a ultra sonic distance sensor for water tank level measurement
temperature sensor, gas sensor, flame sensor with ability to control solenoid gas valve,
some relays, a stepper motor for curtain (forward reverse motion).

controlled by Bluetooth and android.

willing to pay reasonable $, if someone really spare some time to design this system.