A while back, I was wondering about IV checkers. The current standard is, as far as I know, Metalkid's, because it can use Rare Candy information to pin down the IVs more accurately. However, there's a lot more information out there that can help pin down IVs; Metalkid's also handles Hidden Power type, but perhaps the biggest source of information is the RNG. Pretty much anyone who's tried to make a Shoddy team with a legendary knows about the IV/Nature restrictions that the RNG places on them; for instance, you can't get a flawless Adamant Method 1 legendary (which is most of the non-event legendaries in the game). The same applies to other less interesting Pokémon, too, from flawless right down to awful IV sets, and can be used to narrow down the possible combinations of IVs.
There are other ways to narrow down IVs, too. If you know the time at which you pressed "Continue" to start your current session at playing the game (not all that accurately; like RNG Reporter, my checker only needs the minute), that clamps the possible RNG seeds down dramatically; people who are IV checking to determine how their RNGing went wrong are definitely going to know this, but it's a plausible piece of information to check whenever you load the game if you're planning to be doing serious IV checking as it is. (People who soft-reset for legendaries the "old-fashioned" way, for instance, shouldn't have much problem checking.) I've managed to IV-check a level 15 Pokémon, freshly bought from Game Corner, down to one plausible possibility (and a few unlikely ones) via this method. Better still, once you've IV-checked one Pokémon in a session, you know what seed it was caught at, and future Pokémon caught without restarting the game can then be IV-checked very accurately even at extremely low levels. This is not useful in most cases, but is very useful when catching Pokémon to determine your frame during RNGing; RNG Reporter can sort-of do this, but not really (it relies on using an IV checker to come up with IV ranges, then plugging them as bounds into RNG Reporter, which is time-consuming and requires a lot of human intervention).
Therefore, I've created an RNG-aware IV checker. Even for a Pokémon which isn't method 1/J/K-created, it's around as good as Metalkid's, although with a rather different interface (it can incorporate all the same information, though). For Pokémon that are, though (that's pretty much all 4th gen Pokémon; the really major exceptions from a competitive point of view are bred and chained Pokémon, and there are a few minor exceptions too), it can help give a more accurate check than any other IV-check method, and it has features to help in RNGing. As a bonus, I've added in an IV-to-PID feature (which is trivially added if you're messing with the RNG anyway), and likewise an IV+TID-to-SID feature (which I'm surprised hasn't been automated on any of the online checkers yet, given how suitable for computer calculation the formula is, although RNG Reporter can do it).
Although I don't have anywhere permanent to host it, the HTML file can be downloaded from http://filebin.ca/gksxq/method_1_IV_finder.html and viewed locally. It's still a work-in-progress at the moment; originally, I just made it for my own benefit (I'm experimenting with unusual forms of RNGing), but I realised it would be useful for other people too, so here it is in C&C. Let me know what you think (or just lock the thread if I'm really off-topic here...)
There are other ways to narrow down IVs, too. If you know the time at which you pressed "Continue" to start your current session at playing the game (not all that accurately; like RNG Reporter, my checker only needs the minute), that clamps the possible RNG seeds down dramatically; people who are IV checking to determine how their RNGing went wrong are definitely going to know this, but it's a plausible piece of information to check whenever you load the game if you're planning to be doing serious IV checking as it is. (People who soft-reset for legendaries the "old-fashioned" way, for instance, shouldn't have much problem checking.) I've managed to IV-check a level 15 Pokémon, freshly bought from Game Corner, down to one plausible possibility (and a few unlikely ones) via this method. Better still, once you've IV-checked one Pokémon in a session, you know what seed it was caught at, and future Pokémon caught without restarting the game can then be IV-checked very accurately even at extremely low levels. This is not useful in most cases, but is very useful when catching Pokémon to determine your frame during RNGing; RNG Reporter can sort-of do this, but not really (it relies on using an IV checker to come up with IV ranges, then plugging them as bounds into RNG Reporter, which is time-consuming and requires a lot of human intervention).
Therefore, I've created an RNG-aware IV checker. Even for a Pokémon which isn't method 1/J/K-created, it's around as good as Metalkid's, although with a rather different interface (it can incorporate all the same information, though). For Pokémon that are, though (that's pretty much all 4th gen Pokémon; the really major exceptions from a competitive point of view are bred and chained Pokémon, and there are a few minor exceptions too), it can help give a more accurate check than any other IV-check method, and it has features to help in RNGing. As a bonus, I've added in an IV-to-PID feature (which is trivially added if you're messing with the RNG anyway), and likewise an IV+TID-to-SID feature (which I'm surprised hasn't been automated on any of the online checkers yet, given how suitable for computer calculation the formula is, although RNG Reporter can do it).
Although I don't have anywhere permanent to host it, the HTML file can be downloaded from http://filebin.ca/gksxq/method_1_IV_finder.html and viewed locally. It's still a work-in-progress at the moment; originally, I just made it for my own benefit (I'm experimenting with unusual forms of RNGing), but I realised it would be useful for other people too, so here it is in C&C. Let me know what you think (or just lock the thread if I'm really off-topic here...)