2. The Battle Frontier IV guy (only in E)
In Emerald, you can check your IVs by speaking to a man who lives in a house just above the Pokémon Center of the Battle Frontier. He will give you an overall judgment of all the IVs and the best IV of one of your Pokémon.
He will say the following:
“Ah, youngster! Do your Pokémon's abilities intrigue you? Here, here! Let's have a look at your Pokémon!”
You then choose the Pokémon that you need its IVs checked. He will then say:
"...Hmm...This one, overall, ..."
and then one of the following four:
"I would describe as being of average ability. "
-> the total of the six IVs is a number between 0 and 90 (average IV is between 0 and 15)
"I would describe as having better-than-average ability. "
-> the total of the six IVs is a number between 91 and 120 (average IV is greater than 15 but less than or equal to 20)
"I would say is quite impressive in ability!"
-> the total of the six IVs is a number between 121 and 150 (average IV is greater than 20 but less than or equal to 25)
"I would say is wonderfully outstanding in ability!"
-> the total of the six IVs is a number between 151 and 186 (average IV is greater than 25)
Then the man will proceed to mention the best IV that Pokémon possesses. If it has more than one best IV, this will be random. Talking to the man repeatedly will make him speak about the other equally best stats.
"Incidentally, the best aspect of it, I would say, is its (HP / ATTACK / DEFENSE / SPECIAL ATTACK / SPECIAL DEFENSE / SPEED) ..."
He then gives a judgment about that IV alone:
If the IV is between 0 and 15, the man will say: "That stat is relatively good."
If the IV is between 16 and 25, the man will say: "That stat is quite impressive."
If the IV is between 26 and 30, the man will say: "That stat is outstanding!"
If the IV is 31, the man will say: "It's flawless! A thing of perfection!"
The man will then finish up his monologue with the words: "...Hm... That's how I call it."
This Emerald feature is very handy to check if your Pokémon has a perfect IV.