Fi Series 3+ GPS dog collar: best where AT&T is strong, and the plan is the real cost

Research-based review: Barked has not tested the Fi Series 3+. US prices checked on Fi's site November 11, 2026; they may change. No sponsorship, gifted product or affiliate links.

If your dog slips out an open gate, the Fi Series 3+ sends an escape alert once it leaves the safe zone you set, and Lost Mode then tracks it every few seconds, Fi says. It makes sense where AT&T is strong. The catch is the plan: the collar does nothing without one, and from year two the plan costs more each year than the collar.

At a glance

• Suits: owners who want escape alerts and long gaps between charges
• Main advantage: Fi estimates up to three months per charge for a mostly indoor dog
• Skip if: the coverage map shows gaps where your dog roams, or you won't allow Always location
• Main catch: the required plan renews at $189 a year
• Price basis: $129 collar; $228 for year one

Cost

You pay for the collar at checkout. The plan starts when you activate, or automatically seven days after shipping if you haven't. Fi's store lists a discounted first term, then renewals: six months at $59, then $99; one year at $99, then $189; two years at $189, then $339. One year is the default; you get seven days after activation to switch, first terms have a six-month minimum, and plans renew automatically.

Year one is $129 plus $99, or $228, with free shipping. Code SALUTE (30% off, through November 12) makes it $90.30, plus $9 shipping (charged under $100), plus $99: $198.30.

Fi's free trial costs more: $10 shipping, then $129 and $99, or $238, for a certified pre-owned unit. It's for new members only, takes no other discounts, and starts a prepaid year seven days after the 30-day trial, renewing at $198. Cancelling costs a $9 return label, and returns arriving more than 14 days after the trial ends cost $100.

Coverage and battery

The Series 3+ reports over AT&T's LTE-M network; your phone can be on any carrier. Fi tells buyers to check the coverage map first and warns it doesn't show signal strength.

Fi requires phone location set to Always; it says it uses it only while connected to the tracker, costing a few percent of phone battery.

The Fi app holds 4.65 stars from 42,438 US App Store ratings, but 89 of the 150 most recent US reviews (May 31 to November 9, 2026), which mix devices, gave one or two stars. About half of those mention location or Always; others cite cancelling, battery, support, app updates and the base. Version 3.149.1 shipped November 6.

The base handles location at home and needs 2.4 GHz Wi-Fi. Away from it, Fi estimates up to two weeks per charge for a dog outdoors most of the day, and about two days in Lost Mode.

Fit

Fi's pages differ on size: its gift guide calls the Series 3+ best for medium to large dogs, while the collar page says "even on the smallest dogs," and an XS band (sizing chart) fits dogs under 10 lb. The tracker weighs 47 grams, about 1% of a 10 lb dog's body weight. For very small dogs, the 16-gram Fi Mini is the lighter option.

Fi says the steel frame can sustain 500 lb of static pull and recommends adding a harness for pullers. We found no independent test.

Other options

The Fi Mini ($99, same plan prices) runs on Verizon, for areas where that network is stronger. It clips onto most collars and harnesses but lasts up to two months per charge by USB-C, with no base or night light. The $299 Fi Ultra is a separate T-Mobile and satellite tracker with two to three days of battery.

The decision

Check the coverage map where your dog roams, then test escape alerts inside Fi's 30-day return window, extended to January 15 for trackers bought November 2 to December 14. Request a return authorization in time; returning cancels the plan, and shipping isn't refunded.