If you're like me, already have Ecobee(s) but want to add more sensors then here is the deal I came across.
2 sensors for $57.99, probably the cheapest price in the last 1 year, if you exclude YMMV prices.
Quick And Easy Pairing With Your ecobee
Just remove the battery tab and the pairing process will start with your ecobee.
Room sensors are compatible with ecobee4, ecobee3 lite & ecobee3
Long Battery Life
The wireless room sensor uses a coin cell battery that lasts an average of two years and is easy to replace. You will receive an alert if the battery is running low.
3 years limited parts and labor.
If you need to know how/why/if they're better than Nest, pls do a search on the forum. Many other Ecobee threads have great info.