[Krakatao]

I tried this today expecting it to be very hard to figure out what your chocobos reaction would mean with regards to your closeness to the chest. It turned out to be very easy since they tell you in parenthesis exactly what your choco's reaction means. After you use the special grass the map will automatically pop up showing the marker. I rode down to it and stood almost EXACTLY on top of the marker before I dug my first dig. the reaction shows up in the log "Kweh". I move a little then:
Kweh?
(The chest is close)

So that shows that the marker is just a rough indication.

I move agai0n and it goes back to just "Kweh". Anyway, I move a few more times and I get the message:
K-KWEHHH!
(You're right on top of it)

So I dig 3 more times on that exact same spot getting the same message two more times until the 4th dig when and I get:
Kweh! Kweh! Kwehhh!
(You've found a treasure chest)

The chest appears next to where I was digging, which I thought was a little odd. I had to dismount to open it up and I get "a bottle of photoanima" which goes for 4.5k on kujata and hardly ever sells. I was a bit distressed that the chest had to be opened up manually making me think it just might be possible to steal someone's chest, but I doubt SE would do that, right?

The digging does not cost gysahl greens.
Being far away from the chest gets you the message "..." which is basically no reaction at all.
Possible maximum digs: 19 (?)

Additional info: http://wiki.ffxiclopedia.org/The_Chocobo_Hot_and_Cold_Game

If everyone else posts the item they got together with the zone they dug in I'll edit the OP with a list of them all.

-Treasure-
Prairie Chocograph
[blue]La Theine Plateau:[/blue] Photoanima, Parasite Worm, Fresh Mugwort, Moorish Idol, Mushroom Locust, Giant Bird Plume, Whistle Coupon, Helmet Mole, Chocolixer, Aluminum Ore, Raxa
[blue]Secondary: [/blue] Blue Peas
[blue]Konschtat Highlands: [/blue] Parasite Worm, Fresh Mugwort, Raxa, Zebra Eel, Armored Pisces, King Truffle, Giant Bird Plume, Red Terrapin, Photoanima, Aluminum Ore
[blue]Secondary: [/blue] Gysahl Greens
[blue]Tahrongi Canyon:[/blue] Moorish Idol, Parasite Worm, Celerity Salad, Raxa, Zebra Eel, Whistle Coupon, Aluminum Ore, King Truffle, Red Terrapin, Mushroom Locust, Giant Bird Plume
[blue]Secondary: [/blue] Blue Peas, Gausebit Greens

Bush Chocograph
[green]Meriphataud Mountains: [/green]Glass Sheet, Celerity Salad, Dragon Meat, Parasite Worm, Silver Shark, Titanicus, Dragon Talon, Dragon Scales, Rhinochimera
[green]Pashhow Marshlands: [/green]Freshwater Set, Parasite Worm, Chocolixer, Saltwater Set, Dragon Scales, Dragon Talon, Celerity Salad, Glass Sheet
[green]Jugner Forest: [/green]Silver Shark, Celerity Salad, Dagon Scales, Saltwater Set, Whistle Coupon, Parasite Worm, Glass Sheet, Rhinochimera, Dragon Talon, Dragon Heart, Titanic Sawfish, Freshwater Set

[ReinheartTitan]

Well SE did say that you didn't need to use Gyshal Greens. =/

[MisutoVapira]

I went to play chocobo Hot&Cold in the Highlands a few minutes ago.
It was pretty easy, found the chest in like 10-15 digs, dismounted, opened, got a Parasite Worm.
Fun Stuff, finally a fun mini-game~

[AlrinKharr]

Gave it a shot in the Meriphataud Mountains, found my chest after 10-15 digs. Got a Glass Sheet, sells for 10k on Cerberus.

***Update***

Fresh Mugwort - La Thiene Plateau
Aluminum Ore - Konschtat Highlands

[locketaru]

You guys never played FF9? <.<

[Auraeon]

I loved this in FF9, I may have to go go try it now, hopefully my chocobo didn't run away again. <_<;

[Criffin]

I got a fresh water set from pashaw marshlands.

[Fendasis]

I got a Silver Shark from Jugner Forest... I equipped my Narval and ate it :O_o

[Icewolf]

Hey is this anything like the hot and cold game in ff9? Because I was very addicted to that game...and i'd like to get addicted to this one if it is the same lol.

[Krakatao]

Keep'em coming.

[Krystia]

Choco digging and the Hot 'n' Cold game were 2 different things.

Hot 'n' Cold, I remember, was a fast game with a time limits though fun.

[Mewten]

I found a Moorish Idol in Tahrongi Canyons.. it's a fish >.>

[Corrderio]

I got a parasite worm in La'Theine Platieu

Sorry if I spelt that wrong, I'm half asleep.

[Krakatao]

New updates and purty colors. Got a parasite worm today in tahrongi. It appears that parasite worm is available in all prairie chocograph locations. It's probably (I'm guessing) gonna turn out to be the most common treasure. As for the bush chocograph locations, it looks like the rewards are synthesis materials for an aquarium. Still too early to say until we see what else gets dug up.

[Ronberku]

I got a "moorish idol" from la theine plateau. Btw does anyone know how long you have to wait to repeat this game?

[Tsunanko]

La Theine, Fresh Mugwort. Goes for 8-10k per piece at the Jeuno AH. I'll take it...

[Krakatao]

you have to wait 24hours before you can use he special grass agai. I'm not sure if you have to wait that long before you get offered it by the npc, but the update details said 24 hours.

[Marryth]

I got a Parasite Worm in the Marshlands.

[Ryvre]

I played this last night in La Thiene. I went to where the ??? is marked on my map, dug, and got "...". I got nothing but "..." no matter where I dug until my chocobo was fatigued. Maybe my chocobo was confused, he does get lost a lot when delivering messages. Oh, and he doesn't like me very much, I couldn't log on for about a week.

[Icerat]

Wow, you can get Fresh Mugwart quite frequently by harvesting....at least I do. Anyhow, how do you play this game? Like where do you start it, who do you talk to ect. The Chocobo Stables does not seem to offer it.

Thanks for the help.