Tiling Tool is more or less a light version of Pattern Maker. It can create a pattern from only 1 single tile (and that's all it does), including several options for repeats, reflecting and color changing.
The purpose of Pattern Maker is to create grid/half-drop patterns from a collection of clip art. Tiling Tool is better when you have one seamless (or even non-seamless) tile / image and you want to fill the entire canvas with it.
It's included as a bonus when you buy POD Pattern Maker Complete.