Here's an idea, curious for some feedback:

Make a square of tensioned cable (or rigid rail) boxing in some area of garden/food forest/farmland at a height above the plants. Have 4 modules which maintain position on opposite sides and holds a tensioned wire between them, making a tensioned wire along the x and a tensioned wire along the y. At the intersection of these wires there is a powered doohicky that can act like a spider and drop down onto the plants below and do its work. The power to the doohicky could be cable from either axis.