After 8 months of use, I am ready to review this cheap door and window sensor, that replaced my Shelly Door Window 2.

The Aqara Door and Window Sensor T1 is cheap, but comes highly recommended when looking in Home Assistant forums. I had a Shelly Door Window 2 sensor to monitor my garage port status, but it was unreliable. Some times it was unavailable in Home Assistant for hours or days, and other times it wouldn’t detect a status change and just stayed in the old status. It might be a problem with the wifi connectivity, but the signal was OK. Changing to Aqara T1 also meaning going from wifi to ZigBee connectivity, and that should help both reliability and battery time.

When comparing the size, there is a huge difference between the two, and the Aqara T1 will definitely be easier to fit in.
The sensor measures 41 × 22 × 11 mm.

Parring the Aqara T1 with Home Assistant through Z2M is super easy like most ZigBee devices is. You might wanna consider doing the parring in the same physical place you will be mounting the sensor, to make sure it takes the best route. I never had problems with this, but some have.

Changing the battery is very easy. And if you make sure to just stick the back of the sensor to the mounting location, you can leave the back of the sensor mounted while you change the battery.
The battery is a CR1632.

You mount the sensor using the provided sticker, and of course you mount the provided magnet or another magnet on the moving part of the door, window, garage port, or whatever you want to monitor.
The magnet needs to be within 22 mm of the sensor to change the status to closed.

I am very pleased with the performance of this sensor. It´s super reliable, and it sends the status change immediately to Home Assistant, meaning you can with peace in mind use this in automations, like I do with the Adaprox Fingerbot Plus and Actionable Notifications.
After 8 months of use the battery is still showing 100%, so the claim of 2 years battery life during normal usage, seems very plausible.
I haven’t done a single adjustment or reset of the sensor/magnet since installing it, and that´s how it´s supposed to be, if you ask me. That kind of stability is very important when you fill your house with sensors, and begin to rely on them.

Conclusion:
The Aqara Door and Window Sensor T1 is a cheap, but very reliant sensor. This is the kind of sensor you want in your smart home, because it´s easy to install, require almost zero maintenance, and gives instant status updates to Home Assistant. This sensor might not be the newest sexiest thing on the marked, using fancy new protocols or technique, but it has already been deployed to massive scale, and all the small bugs have been fixed, leaving you with a very good ZigBee sensor, and for some, that´s way more important.