When you are married to a landscaper (or contractor, or builder) there are always tape measures lying around. My boys loved playing with tape measures, but I could never take my eyes off of them for a second, because a real tape measure releases really quickly and can snap back on small hands, fingers, or eyes. They can also be sharp with metal edges.
The tape measure shown above is soft and rolls back up with a turn of a knob. It shows both inches and centimeters and has a nice 1 inch width with easy-to-read numbers. These tape measures can be used to measure all sorts of things in the classroom, as long as they are less than 5 feet long. That means that children can measure their heights (unless you have some extraordinarily huge three year olds in your program). They can measure furniture, rug space, the edge of a desk, and the width of the easel. Remind children that inches and centimeters are standard units of measure, and that they are the same everywhere in the world
Try to give children a place to record their measurements, and help them write them down. They can copy the numbers they see on the tape measure which will reinforce their sense of number as well as support their fine motor skills.