How common is it for someone to need a capsule endoscopy?

Depends on the reaso: Capsule endoscopy is a useful noninvasive procedure to look at the small intestine. The frequency of its use depends on the indication. The most common indications are concern for a bleeding source in the small intestine, or concern for polyps/cancer, or crohn's disease. For these indications, it is used pretty often.

Sometimes: Capsule endoscopy is very useful to help diagnose causes for anemia, small intestinal polyps, or inflammatory bowel disease.