Be very very careful with 3rd party warranties. most of them have serious fineprint so comb through every word thoughtfully on them. the most common gotcha's I've seen are:
1.) limits on repair costs - i.e. Max $2000 for blown engine, won't cover a fraction of the actual cost of BMW engine swap.
2.) Not to exceed the face value of the warranty on some really shady ones
3.) Repair facility choice limits - no dealers, only shops in their network
4.) Part choice limits - like no OEM parts, only aftermarket parts they will cover, you want that BMW part for $950 but they will only pay out the 3rd party part for $175
5.) some make you pay your own repairs then file reimbursments later which takes a while and may get rejected
6.) Labor rate limits - BWM here is like $172/hr... they may only give allowence for $65/hr
Typically - there's a reason they are in the business of selling warranties - to make money, I have not stats so I'll make one up
I would say for every time a warranty worked out good for someone, 50 people got ripped off and another 50 didn't use it. They are mostly house-favored odds.
Between personal, family and immediate friends - have experience with about a dozen or so of us. had 2 good wins where they were thankful - most never used it... had one really bad experience on limited max payout for a blown tranny that was something like $1200 when it cost $6000.
The OEM ones are usually worth it, like BMW, or going through CarMax I've heard good things on from a few close friends, actually both those wins I know of were both through carmax.