Fi Series 3+ Smart Dog Collar

A GPS tracker built into a collar, with live location, safe zone escape alerts, activity tracking and an LED light, on a paid GPS/LTE plan.

Who it suits

Owners who want a slim all-in-one GPS collar that tracks walks automatically and has long battery life.

Key facts

• Up to 3 months of battery life with wireless charging (Fi)
• Rated IP68 and IP66K; Fi says it is tested in fresh and salt water (Fi)
• All-in-one collar with LED lights and a stainless steel frame; modular sizes from XS to XL (Fi)
• Live GPS tracking over LTE-M, safe zone escape alerts and a lost dog mode, powered by a GPS/LTE plan (Fi)

What reviewers say

Treeline Review: Jae Thomas tested it on their own dogs for Treeline Review (updated August 2026) and named it best for advanced activity tracking and a close runner-up overall. The battery lasted about 10 weeks, safe zone exit alerts were accurate, and it tracked walks and told walks from drives on its own. Location was slightly less accurate and slower to connect than the Tractive, it uses one cell network (AT&T), and the included collar did not hold its adjustment well. Treeline Review does not say whether the unit was a maker sample.

We did not test it ourselves.

Pros

• Very long battery life
• Tracks walks automatically
• Slim, low-profile design

Cons

• GPS/LTE plan required
• Single cell network, per Treeline Review
• Included collar loosens, per Treeline Review

Good to know

• Location depends on cell coverage; keep an ID tag on and your microchip registration current.
• Fit the collar so it is snug but not tight, and check the skin underneath regularly.
• Activity numbers are not a health check; ask your vet about any change in your dog’s energy or behavior.