We use a 3rd party app called Pushover to allow for this feature.
Once the app is downloaded, you are assigned a unique user id and an email address for your phone.
Go to PuppetVendors, create a new vendor account as usual but use the email address provided by the app this time. (here's the format: email@example.com)
Make a test order with items belonging to the vendor
Wait to receive the push notification