As far as I can see, these smoke detectors are only available as a set, but you can also add the other X-Sense smoke detectors to the system.

The batteries are included

Hello, According to my research, no. You need to buy a six-piece kit + 4 units separately.

The difference between the XS0B-MR61 smoke alarm set and a general X-Sense smoke alarm set lies primarily in the networking capability, the app control and the voice output. The XS0B-MR61 set offers networking via a base station with up to 50 devices and a range of 500 metres, app control for status checks and alarm muting as well as a voice output that indicates the location of the fire. The alarm has a volume of 100 dB. The set is also supplied with 6 smoke detectors. In comparison, other X-Sense smoke alarm sets are often less networked or have no voice output, and the number of networkable devices and the range can vary. The XS0B-MR61 is specially designed as a smart Wi-Fi smoke alarm with app notifications and voice alarm, which sets it apart from simpler sets.

Yes, the base station is included in the package. Top product. I can only recommend it. I also have the Termo hygrometer and the water detector. Everything runs via the same station.