-There is another two Pokéthlon events.
It appears that you'll have your three Pokémon across from another three Pokémon. This is essentially a Snowball Fight called Shooting Snow. Another Pokéthlon mode is called Ring Out Fight where your 3 Pokémon have to knock the other three Pokémon out.
-PokéGear will be in games, appearing in the Menu as usual.
It contains the same features as before specifically the Phone, Map, Radio & now the Itemfinder. -It also shows the capturing of Pokémon on PokéWalk.
-You can also register two key items in this game and they are accessible via the Touch Screen.

Pokémon Sunday clarified a further Pokéthlon details.
Firstly, your Pokémon are rated based upon several bits of criterea including Speed, Stamina, Power & Jump.
Secondly, two of the Pokéthlon events are known.
-First is Dash Hurdles which runs like a standard sprint. Your three Pokémon are all controlled by you and you have to tap the Pokémon to make them jump in time, allowing for them to continue. The quicker you do it in, the better your Pokémon score.
-Secondly is the Bound Field. This one features your Pokémon on a trampoline. There are numerous gold targets on the top screen and you have to make the Pokémon jump up to hit the targets.

From CoroCoro and Pokémon Sunday,
Here are the news:

1) Red Gyarados remains at the Lake of Rage and is at level 30.
It appears that it will be raining when it is encountered.
2) When Surfing, you appear with the icon of standard Surfing like DPPt.
3) Eusine from Crystal appears in the story based on the Legendary Beasts.
4) Nine games that utilize the touch screen of the Nintendo DS will be in the game.
-One of them is named Pokéathlon, there is a special building in Goldenrod City.
5)
a) Ho-Oh (HG/Tin Tower) and Lugia (SS/Whirl Islands) will be level 45.
b) They will be Level 70 in opposite games.
artwork of the Pokémon Entei, Raikou and Suicune, as well as Eusine.
7) Entei, Raikou and Suicune will roam Johto at Level 40.
8) Overworld sprites of the said Pokémon in the Brass Tower can also be seen.
9) Part of Lugia's sprite can also be seen.
10) The Kimono Girls will have roles in the storyline and will be met several times.
11) Legendaries Pokémon: Mewtwo in Cerulean Cave, Latios (HeartGold) and Latias (SoulSilver) roaming Kanto.

The official site, http://www.pokemon.co.jp/special/hgss/special/movie.html has just updated with some new footage of the upcoming HeartGold & SoulSilver from the trailer being shown around Japan. This footage does not bring much new but does show us a variety of areas including inside gyms and the fact that the Pokémon that follow you can easily use HM moves.