For use when turning a dog loose for a limited time, it's hard to beat the Garmin astro.... except for price. My area is so rugged I get about a mile with it. It's a bit big for my dogs, and you can't really leave it on 24/7.
Tagg is great for something that stays on the dog 24/7. Battery life is a couple of weeks for me. But, the area I hunt in Wyoming does not have good cell signal. You cannot suspend service, once you activate it, you have to keep the service plan. It's just under a hundred dollars for the docking station and one collar unit, and the service plan is 7.95 a month. It also has an activity monitoring feature.
Marco polo is sort of like lojack, you don't see the dogs location on a map, it has a beep and directional arrow on the handheld that you use to locate the dog. You can set a boundary around the handheld unit so it will alarm if the dog leaves the area. It can stay on the collar and battery life is over a month. No service plan since its not cell assisted GPS. Range is maybe a mile or a little less in my area. It's around two hundred dollars or so.
When I travel out west, I have tagg and Marco polo on them, but once we get out in Wyoming the tagg isn't much good. When I turn them loose on a jackrabbit one is wearing the Marco polo and the other one is wearing a Garmin. My family uses the tagg to track me so the know where I am at during the long road trip.

Samantha, I looked though the pocketfinder website FAQs and didn't see any info about suspending and resuming service. On the site I login to locate and configure the device, it asks you to call support to cancel or suspend service.

The device, when purchased from apple.com anyway, comes with 2 months of free service and there is no contract. I would suspect that you could put it in a suspended state or cancel and resume whenever you like, like a prepaid cell carrier; that's basically what it is. I'd think that you'd pay in monthly intervals so if you turned it on, you'd pay the $12.95 for that month.

Kiersten, Vickie, thanks for the info on the Garmin devices. It sounds like they'd be well suited to coping with my concern of my pup running off on a hike. I just wish they were cheaper

The Marco polo might be a lower cost option, and is small enough and with a long enough battery life to stay on the collar all the time. While it doesn't do GPS things like show the dogs location on a map, if a dog is lost it can take you the dogs location, and does not rely on cell phone signal.

 Quote: Bryan Simms

Kiersten, Vickie, thanks for the info on the Garmin devices. It sounds like they'd be well suited to coping with my concern of my pup running off on a hike. I just wish they were cheaper

I've actually seen these (I guess used) on eBay!

They are on the 4th version, so sometimes you can find older models for sale. The problem is if it's from a coonhunter it's been used hard. They use them because it tells you in almost real time where the dog is, you can watch the dog icon moving on the screen, and you can tell if he's moving or standing. Later you can download his tracks and see where, how far, and how fast he was going.
If you look for used, the dc 20 was harness mounted but had a plastic bracket to mount on a collar. The dc 30 and 40 were permanently collar mounted. You could use the same Garmin handheld for these. But the newest one uses its own handheld and doesn't work with the older handhelds.