a) Fire detectors. 13 units including the central. (Basically one in every room where something may conceivably catch fire.)
b) Leakage sensors in any room with faucets or washers in it - 7 units.
c) Kitchen appliances - 5 (Cook top, two ovens, fridge, freezer)
d) HVAC - 7 units (Central ventilation. Heat pump. A handful of electrical panel heaters.)
It quickly adds up - at least if you live in the boonies where land is effectively free.
Interestingly, at one of the largest Danish chains, it's listed under "American fridges", most of those DO have wifi. If you just pick: "Fridges", then none of them have wifi.
That aside, I fail to see any reason why any user would want their cook top to be accessible via an app.
On the contrary, if the cook top is switched on, I very much prefer to be in the immediate vicinity.
They have backup batteries and form their own mesh network which works independently of the main WiFi.
If the central unit disappears, the detectors still all go off if one is triggered. (Central unit offers app interface and optional 4G fallback network connection.)
Some of IoT device you list I’d actively avoid, but thinks like robot vacuums is really useful.