I try to create alarm with HA. Trying to find cheapest solution.
Alarms with envisalink or some MQTT are quite expensive. I think the best way would by couple of motion detection sensors (PIR). Are there some cheap wireless (mqtt ot other protocol) sensors you can reccomend?
Note that these sensor doesn’t ask for a receipt acknowledgement, they are just sending a signal several times when they have to, if the signal is not received nothing happen. In my usage it is ok with this constraint, for certain people it can be an issue.
How cheap do you mean? Attaching a PIR to you Pi only cost a couple of quid. Tricky part in my experience is getting presence detection to work so you don’t constantly receive notifications. I have the Philips Hue PIR sensors in my house for lighting, so just use these, kill two birds with one stone