Drain and rinse the kelp noodles and place in a large bowl. Add enough hot water to cover (hot water from the tap is fine, it doesn't need to be boiling) and set aside for 30 minutes.
Meanwhile, combine peanut butter, sesame oil, ume plum vinegar, honey and water in a small blender or food processor and blend until smooth. Add more water to thin out, if desired.
Place a steamer basket over a pot of boiling water. Add vegetables, cover, and steam for 3-4 minutes, until crisp-tender. Transfer to a bowl.
Add shrimp, cover, and steam for 2 minutes. Remove from heat and transfer to the bowl with the vegetables.
Drain the kelp noodles and place in a clean, dry bowl. Pour the peanut butter sesame sauce over the noodles and toss to coat. Add the vegetables and steamed shrimp, and toss again. Serve immediately, or chill and enjoy later.