I think you are looking for a Sit'nStroll carseat stroller. I haven't seen any here in Singapore except those that were bought in the US and brought over. I have one and loved it! It goes up to 40#s and is certified for air travel.
You can do a search on it on the web. I saw it for about US$200. It's well worth it if you intend to travel with a baby/child up to about 4. If you are going to get a seat on the airplane for your wee one, get it! He/she will be comfortable on your trips.
Although it advertises that you can pull out the wheels while the baby is in the carseat, I found it cumberson to do it alone. I think it's safer with someone holding the front up while you pull out the wheels from the back.