AFAIK there is no such product for sale as an "extended warranty"
In America, these products are legally called "service contracts" or "service plans"
Most of the time a "factory sponsored" service contract/plan is cheaper at initial purchase of the car.
Many of the factory sponsored plans can be purchased later but before the initial factory warranty is expired. Buy this way usually costs $100-250 dollars more.
Some factory sponsored service plans can be purchased after the initial warranty is expired but they are even more expensive because you end up paying the "used vehicle" pricing.
Third party plans are the most problematic in that they almost always have deep exclusions, and most of them require pre authorization before any repair is started, additionally many of them require the service or repair to be done by someone in "their network"... Internet RV forums are full of horror stories on every third party plan provider you can name... there are also a LOT of horror stories about the Factory plans also
Edmond's and other auto buying sites all agree that these products are one of the highest profit areas in car sales. They also advise against third party plans. They note that Factory plans have the least amount of hassle getting a repair done
Because of the very integrated safety, emissions, and power management computers and other electro mechanical devices on the Smart car, I assume that any service plan will be a bit expensive...I bet right now the very least expensive one will be in the $700~900 range
I now buy the Ford Gold ESP plans on the high-end trucks that I have decided to keep for 5 or more years.... and I buy just before the 3/36 is expired.... I accept the extra $100 cost of waiting...
In the past I have passed on the extended service plan only later to have a Major multi system failure.... $2359.99 for the plan or $7984.99 for the repairs out on the road (yes Virginia a burned up Ford 4R100 auto trany can get damned expensive)
One F250 truck cost $1984 for the Gold plan and I never used it. When the truck was totaled FoMoCo gave me back a prorated $1250.
This current F350 the Gold ESP was $2300 negotiated down from $3680 because I am a good customer... I know other folks who got deeper discounts... point is they are usually NEGOTIABLE!
I plan of modifying the Lil Smart so 2/24 is OK with me
I doubt I will sell her any time soon (unless I get some insane high bucks offer out of the blue) so I will decide later if extended service contracts make sense
I am still researching but one of the Brit sites have a guy from Smarts R Us claim that
ALL 450-451 transmissions had an internal oil seal that craps out in the 50K mile range.... sounds labor intensive to fix a cheap part... can not tell yet if it trashes all sorts of other things... I hope he was just assuming the 451 trany would have the same problem.....
Either way we have a ways to go to see if the 451 is reliable or problem child.... decisions on extended service plans are going to be a hot topic in these forums