Can several bluetooth devices be seen as one unique device from the point of view of an Android smartphone?
Unfortunately, it is impossible with regular bluetooth. During pairing, secret cryptographic keys are exchanged between the phone and device; even if you could make few bluetooth devices have the same address, the keys will not match.

BLE (Bluetooth Low Energy) has a "Broadcaster" profile, which seems like exactly what you want:

https://thenewcircle.com/s/post/1553/bluetooth_smart_le_android_tutorial

One really cool feature of Bluetooth LE is this role of a Broadcaster, or a device that does not accept incoming connections, but rather pushes out the data is has inside its device discovery, or advertisement, data

Unfortunately, using BLE requires a Bluetooth 4.0-capable chip as well as a BLE-compatible smartphone.