Indoor Active Play for nearly four year olds

Hello All -- I have a couple of very active kids -- b/g twins who will be 4 in Sept. and I am going to go crazy unless I figure out an alternative to their jumping from one piece of furntiture to another -- they are nonstop. And this is after I take them to the playground! I am thinking of some piece of equipment or bean bag or something they can jump/climb/burn off steam with in the apt that is relatively safe. I saw these interlocking foam shapes at the Science Fair last week at Washington Square park but can't seem to find anything like it on line. I am also considering some kind of contraption for the doorway. Anybody with any solutions/experience with this? Much appreciated.

some random stuff:

http://www.bilibo.com/en/intro/

these can be used as stepping stones (or jumping spots)

http://www.amazon.com/Champion-Sport...8027016&sr=1-1

http://www.amazon.com/Bobles-001-01-.../dp/B001M4SKC8

How much room do you have?
We have a basement playroom and have a small trampoline - the kind that has a handle you hold and a plastic slide (designed for outside). Other things I've seen from friends with VERY active boys: a plastic climbing playhouse (designed usually for outside) in a corner of their basement - actaully looks nice and unobtrusive. Ikea swing mounted from bedroom ceiling. And they play putside all the time no matter what the weather!

ETA: Ok just saw you said "in the apt" so assuming not much room. The trampoline isn't huge but it does take up valuable floor space - the swings don't use floor space at least.
Not seeing swings on the website now..
http://www.ikea.com/us/en/catalog/products/00041048
http://www.ikea.com/us/en/catalog/products/40054072
http://www.bonanza.com/listings/NEW-...HOOKS/15277508
http://www.amazon.com/Pure-Fun-40-In...069320&sr=8-33

My girls do use the bilibos a lot as stepping stones, spinners etc. That was my first thought when reading your post. Other than that, we just have to get outside a lot.

hulabaloo
yo baby kick flipper http://www.garagecotoys.com/
basket ball hoop on the wall or back of door http://www.amazon.com/SKLZ-Pro-Mini-...8073071&sr=8-1
hyperdash
honeybee hop http://www.amazon.com/Hasbro-34888-P...8073092&sr=8-1
mattresses on the floor
plasma car

Probably not really what you were thinking of but the Prima Princessa ballet DVDs have been a hit here (just to prompt some dancing on the floor - no extra equipment needed). We have Swan Lake and The Nutcracker http://www.amazon.com/s/ref=nb_sb_ss...+princessa+dvd
and DD and DS both love them. They have excerpts from a professional ballet company doing the ballet, a voiceover to explain the plot in a 4 year old appropriate way, segments where young dancers who are really good show steps properly and parts where a bunch of small children twirl around and have fun. It's really cute.