If you use Zigbee the Aqara and SONOFF contact sensors are both fairly good in my experience.
The Aqara ones are very small and neat, the SONOFF are a bit larger but cheaper.
Home Assistant is open source home automation that puts local control and privacy first. Powered by a worldwide community of tinkerers and DIY enthusiasts. Perfect to run on a Raspberry Pi or a local server. Available for free at home-assistant.io
If you use Zigbee the Aqara and SONOFF contact sensors are both fairly good in my experience.
The Aqara ones are very small and neat, the SONOFF are a bit larger but cheaper.
If you have a Zigbee Coordinator, I'd recommend taking a look a Aqara.
I'll second the aqara sensors. I've got them on all my doors and my dog food container so we don't miss any feedings. ZigBee setup was quick and easy and so far they've been very fast and reliable.
I have a few of those. They work reasonably well, but they can be finicky to get on the network in the first place, in my experience. But I keep buying them so they must not be too bad.
I bought my two sensors two years ago now. Haven't had to replace the batteries yet and no connection issues or anything. I use one of them to turn on the lights at my front door when I open it and it's always done it's job quickly. Z-wave so ofc you'll need a dongle.
$30 rn
https://www.amazon.com/dp/B01N5HB4U5?ref=ppx_pop_mob_ap_share
I've had good luck with this Zigbee one. It's on the larger side, but takes AAA batteries which is nice. THIRDREALITY Zigbee Door/Window Sensor
Alternatively, if you're keen to tinker a bit you can get an SDR and then use 433MHz sensors. (Requires using RTL_433 and MQTT).
I was able to use the existing sensors from my traditional security system this way. Nice thing is that it's the most reliable wireless components on my system and the battery lasts forever.
I would suggest a nooelec SDR like this one: Nooelec RTL-SDR v5 Bundle
And something like this for sensors: Door Magnetic Contact Sensor
I have some cheap ass Tuya Zigbee sensors from AliExpress. In my experience they are reliable, quite small, i sill haven't changed the battery, and they are super cheap. Make sure you get the Zigbee ones, not the wifi version.
tuya means one relies on their API keys right? i just love the m5stack and feel safe about updates and apis for the next decades.
If it's zigbee, that shouldn't be a problem. The tuya headache is their wifi stuff.
ah ok. nice. thank you.
I'm by no means an expert, and I'm not sure what API keys you are referring to. I know that Tuya smart devices usually have two versions, a wifi and a Zigbee one. The wifi ones require you to add them using a terrible smartphone app, and the integration with Home assistant sucks. The Zigbee ones work like any other zigbee device, locally controlled. I have several Tuya Zigbee devices which works great, they are integrated in home assistant using zigbee2mqtt.
ah ok. i just have one tuya fan left and it uses wifi and i thought all tuya have wifi.
only for wifi version, witch shuld be avoided becouse batteries dies fast on wifi.
With these its only via zigbee no outside connecton? the price on these is good.