What about the range in a flat?
e.g. children's room in one corner of the flat > base station in the other corner of the flat.
Does the system work via DECT?
The system works about as well/ as badly as all other systems. "Max. 300m" is probably in the open, in an apartment/ from flat to apartment/ house to house/ flat to garden/ 1st floor in the basement you can simply forget 300m.
The positive thing about it is: If the direct connection doesn't work, you can use the WLAN/Internet on any Internet-capable mobile phone. However, this communication must always go via the Motorola server. How secure this is is questionable, but I don't think any hacker is interested in a sleeping baby.
DECT: Someone posted here that it works without WLAN with DECT. I don't know myself. -> ask google.
All in all a good device. In terms of the whole touch-and-feel, if you don't need Wi-Fi, I would recommend the NUK ECO Control+Video 2.4 GHz baby monitor. A very good device, but without Wi-Fi and without a recording function.