We have covered plenty of lawn care robots in the past. You could always build your own to take better care of your garden. randofo has shared a video that shows you how to build a seed spreading robot. You are going to need a Lynxmotion Tri-Track Chassis Kit, Arduino Uno, battery, rangefinder sensor, and a few other parts to get started.
You can find the instructions for this robot on Instructables.com.