Proof of concept but works 
I saw an article linked on Rachio’s facebook page describing using the Amazon Echo recipe to email a custom gmail address everytime Echo adds something to its To Do list. Then different IFTTT recipes monitor that gmail for certain trigger phrases to trigger a rachio event like water zone 2. So you would say:
“Alexa add water zone two to my to do list” … 15 minutes later 
… IFTTT gmail integration then waits 15-20 min then triggers the recipe to water zone 2. Obviously not great for those of us needing immediate gratification.
If you are into coding (I’m just a hobbyist) there are much more elegant ways directly utilizing Amazon’s Alexa SDK (ASK). Just got the Echo yesterday so still playing, but I was able to get Alexa to talk with IFTTT’s Maker channel to create a recipe to immediately trigger an event to water zone 2 for 5 minutes. So now I say:
“Alexa tell Rachio to water zone 2” … and immediately zone 2 is on!
IFTTT’s Maker channel creates immediate triggers which is the key. Also it’s then quite easy to create custom recipes in IFTTT to test out.
I’m not going to go through the gory details since I’m still playing with it, but if interested here is what I did:
- Become a amazon developer and attach Echo to the developer account
- Create a AWS Lamba account (to host the nodejs code)
- Connect to IFTTT’s Maker Channel and Rachio Channel
- After going through a few of the Amazon Alexa sample codes I basically then modified:
mefogle’s AtoIFTTT nodejs code - Create an Alexa “Skill” based on the code in AWS Lambda and then registered that code in Amazon’s developer portal.
- Create the IFTTT Maker recipe to receive the command when you speak to Echo and then tell Rachio what to do.
as you can see very proof of concept, but oh soooo cool!
This is great, thanks for posting!