BTW, if you do happen to need one more three-way kit, you can get the Lutron starter kit which has the smart bridge, a dimmer switch, a pico, and one wall plate for right around $100. That way the smartbridge itself is only costing you an extra $40 instead of $80. 
https://www.amazon.com/LUTRON-P-BDG-PKG1W-Wireless-Lighting-Starter/dp/B00MXCRAX8
Note however that if you get the plain smartbridge, you will only be able to use Picos as auxiliary switches to Lutron Master switches. That’s OK, they’re still valuable. For that purpose, and you can’t use a GE add on switch for anything except triggering its own master, either.
But if you do want to start going deeper down the rabbit hole, if you get the smartbridge pro you could eventually set things up so that you could use picos to trigger anything that smartthings can do. But it’s a pretty deep rabbit hole and you need some technical expertise to pull it off. And the smartbridge pro is around $150 instead of $100 for its starter kit.
https://www.amazon.com/Caseta-Wireless-Smart-Bridge-Lighting/dp/B01AVLTHY2/
Here’s the link to the project report on setting things up so you can use Picos to control other smartthings events.
Both pro and regular SmartBridge work fine with the official SmartThings integration. The pro just opens up some additional feature possibilities with other integrations.
If you want to use either with HomeKit, make sure the box says “HomeKit compatible” and that it is “generation 2.”
I think most people using SmartThings will be fine with the regular smartbridge. But I just wanted to mention the pro option so nobody says “I wish I had known about that before.” 