The Delfin arm bands actually worked pretty well for use while swimming. I used them over both the Dexcom sensor and pods. They adjust for tightness with velcro that allows a wide range of adjustment, so should work for most. They are a bit difficult to get just right on your own, so helpful to have an assistant do the fine tuning, but once on they are very secure and can stand up to a lot of water activity. The pocket isn't really big enough for the PDM - I didn't actually try since I was going in the water anyway. The pocket is stretchy, but it would be a tight squeeze. I did confirm that the Dexcom G4 will slide right in easily. Anyway, for $20, they did the job I was hoping they would - no pods or Dex sensors lost in the ocean!