Just used this service - fantastic - they pick you up in a buggy as you come off the jet bridge and then take you to their private terminal and clear you for immigration while they retrieve your bags and put them in your car. On the way out, they have private security and immigration. There is also an option to/from you plane by limo across the tarmac.

http://jetquay.com.sg/

Can you tell us the cost and how to arrange this service?

http://jetquay.com.sg/membership.htm

I fear this service will not save you time as the bottleneck at Changi is luggage arrival time. So instead of waiting at the carousel you end up waiting inside a limo. I've never had to wait to clear customs.

http://jetquay.com.sg/membership.htm
There are no prices listed. News reports at the time the service was launched talked of "from S$2000" (IIRC) for a private membership...? That's a pretty hefty price to pay in my book, given how fast even the normal terminal for the plebs is.

Incase it's of interest, I managed to find some single use prices for this service via http://www.worldwideflight.com.hk/form.html

I assume they're priced in HK$ but it's $350 for the Gateway service, $1500 for the Quayside and $6500 for the Jetside.

(prices are per person)