Cell phone or Walkie Talkie for 8 YO DGD

Bass Pro did have somewhat "professional" models that were sturdier in a rubber case for about a hundred apiece. GMRS and there won't likely be a hundred other tourist using the channels. Signal is a little clearer and range greater but not that much, than FMRS. Too bad we can't use VHF like they do in Canada and on the water.

Hug a tree training

We taught our autistic grandson the same concept when at Disney parks. Teaching him to recognize any cast member with a badge he was taught to ask any one of them for help. It paid off one day when we got separated. No panic. We found him with crayons and a Cast Member right at his side. His grandparents were lost, not him.

Forget about the cell phone.

When we were in Yellowstone a few years ago, the ONLY place in the entire park that I had cell service was Old Faithful Inn. There's a cell tower on the hill across from the hotel.

Get some FRS radios with rechargeable batteries. I'd say $50-$70 a pair is a good price. Go on Amazon and read the reviews to get a good pair. I've gone through several brands, and Motorola has been the best so far.

My kids were 11 and 13 when we were there. Never felt any concerns about getting separated, and we did a LOT of hiking.

OP here...What is a reasonable price for decent Walkie talkies (pair)?

Cell service in Yellowstone and the surrounding area is "iffy" at best. A walki-talki is always fun at that age, and can be used when going to the playground, the campground store to get the morning paper (my kids used to love doing that) or just bike riding about the campground. I loud whistle is a better emergency signaling device, can be clipped on clothing, and carried everywhere.

I am in complete agreement with the later answers. A whistle and a radio and a plan - all Three.
I would add (of course being a waterman) The you all do a practice drill every morning. The time you don't want to learn how safety gear works is when you NEED IT. Cell coverage in Yellowstone is problematic at best. A whistle does not need batteries.
If you get a set of FMRS radios, get the kind with rechargable batteries and charge them every night and leave them on all day. Check them every morning over a significant distance. The kid will think it is fun and you will know that they are safe and that she know that she can call to you any time.
It is unfortunate the that Garmin Rinos are expensive. I would have a pair.

Matt

Even though cell service is limited, A cell phone with GPS tracking enabled is also a very good idea.

Also, make sure that everyone (yourselves included) carries identification, preferred photo, AT ALL TIMES! Radios are good, but the whistle is one of the best plans.

I too would vote for the radio; whistle is also a good idea. Also, take a photo (with your phone if you have that capability) each morning. That way you can share exactly what the little one was wearing.

A whistle and teach her to "hug a tree". Stop, find a friendly tree, hug it and stay put.

Radios are a good idea but I would still add the whistle and hug a tree. Forty years in the two way radio business and I can assure you the range will be as suggested at under a mile or even less in heavily wooded areas. Of course, jump in a helicopter and the range becomes line of sight and can go a great deal.