I have an idea for this product but want to make it cheaper and less sophisticated but i do need it to detect light changes. Can arduino be utilized for this a battery powered light sensor that can send notifications to smart phone etc.
In theory yes - although to get WiFi capability and low power consumption will be tricky - standard Arduinos don't have low-power sleep (its the USB interface that doesn't power down).
would you know what i can use instead
Start looking here