I hope I didn’t mislead you by the “fairly inexpensive” mention I made. Typically the Z-wave sensors are in the $30-$50 range & require a Z-wave USB controller.
Zigbee sensors (Xiaomi Aqara for instance) are in the $10-15 range and i believe also require a zigbee controller.
You might want to take a look at ESPHome devices but they generally require some electronics knowledge to wire sensors to boards. The sensors
Here’s a link for a topic on this forum regarding a Fire tablet.