Looks like this topic has been dead for a while... Perks have been coming more frequently lately.
This is what I got:
Level 3
Feb 2019- socks
Level 4
May 2019- postcard
May 2019- $4 off any delivery or pickup order on SliceLife.com
Jul 2019- 20% off each of their next three parking reservations on ParkWhiz
Level 6
Oct 2019- $7 off an audiobook from Google Play
Level 7
Nov 2019- $3 Google Play credit
Dec 2019- $3 Google Play credit
Dec 2019- $30 in bonus credits on Seated (I actually ended up getting a lot more due to a glitch)
May 2020- postcard
May 2020- $10 DoorDash credit & one month of free DashPass
May 2020- Headspace meditation livestream