I subscribe to the NCTM Math Education Smart Brief. In today's edition, there was a short article on two fifth grade math classes who made estimates of the circumference, weight and number of seeds of a watermelon. The students then checked the circumference, found the actual weight and ate the watermelon to find the number of seeds. This gave them real life data to compare with their estimates. As a final step they put the data into a spreadsheet and created a bar graph.
This is a neat hands on activity that I had never thought about. Usually, I do activities with m and m's or skittles but this makes a nice change and could be done outside since watermelon gets rather messy.
I think you could do this with cantaloupe, or cucumbers both of which has a fair number of seeds and are good to eat. I like the teacher included a technology element in the lesson.