Can this hub also be used to extend the existing Aqara Zigbee network (Aqara Hub M2)? Can the signal to activate the alarm also be emitted by another hub, or only by sensors that are linked to this hub? (I'm thinking of buying two of these to use as an alarm on the one hand, and to make sure all Aqara sensors have a good Zigbee signal on the other. Is there also the possibility that the Aqara sensors communicate with their hub via the Zigbee network set up by Philips Hue - this would already be very stable in my case... Thanks for all answers!

Yes, you can network the products in the home. The products can then communicate together. For example, sensors at the left end of the house can communicate with the hub at the left end of the house and sensors at the right end of the house can communicate with the hub at the right end of the house. However, please remember that the internet should not be too far away from the hub, otherwise the hub will not be able to connect to the internet. An example is my Aqara Hub M1S. It sometimes has problems with the Internet and therefore sometimes flashes dark blue until the Internet connection is re-established. Instead of another M1S hub, you can also use a G2H Pro camera hub, which also serves as a hub and can monitor your home at the same time. You don't have to worry about security, because if a product is HomeKit certified, it only has to run in the local network, otherwise it would not be HomeKit certified. So buying a G2H Pro Camera Hub would almost be better than another Hub M1S, as it also has built-in night vision, a built-in motion detector, HomeKit-controlled face, vehicle and pet detection, as well as a 100+ degree field of view. Please note, however, that an Apple iCloud+ subscription is required to have a security camera in HomeKit. However, this is not very expensive at a monthly price of €0.99 for 50GB of cloud storage. However, if you don't use HomeKit, you can also benefit from the above features... However, for the other smart home standards, it's not clear to me whether you need a subscription for security cameras. The decision is up to you. Personally, I would buy a G2H Pro Camera Hub, as it costs only 10€ more or even the same as the M1S Hub on some websites, and is a security camera that takes the Smart Home to the next level.