I have not tested with this company (I don’t have any deceased relatives’ DNA I can access – maybe one day I will find something Mom or Dad touched with enough DNA to go this route). I expect this field to grow. It’s not the only DNA company offering this service. From what I have seen, the prices can vary widely and there’s no guarantee of success. Compared to autosomal DNA testing for genealogy which runs around $100 (with sales as low as $49 on a somewhat regular basis), these other types of DNA samples can easily run in the thousands. There was an article a while back with the expectation that many of these companies will initially run $1,000 – 2,000 or more to test, but with the expectation prices would come down over time.
For the typical genealogical DNA companies (FamilyTree DNA aka FTDNA, 23andMe, LivingDNA, Ancestry DNA, MyHeritage, Helix), they rely on either “spit kits” (i.e., you spit in a vial and send it in) or cheek swabs. However, these tend to require a living person although some funeral homes and mortuaries are now offering to collect DNA from a loved one before the funeral. For deceased people like my parents, I would need to find a licked stamp, possibly a piece of paper they touched, a hairbrush with a hair follicle attached, or something similar that might have a viable DNA sample. It’s important to realize that you can only get so much DNA from a particular sample and each use of a sample tends to shrink what DNA remains to test.