Backlink Indexers are simply sites such as indexkings.com that claim to get your backlinks found by Google faster. The jury is out on how useful they actually are but essentially they place backlinks to your backlinks. Theory being if you have one page with a link you want Google to find you can do a lot better with 800 links to that backlink page. Now it sounds reasonable but is 800 or 1 any different when we are talking about zillions of links on the web?
Ive used both free and paid indexers and ultimately I saw no real marked difference in Google indexing the page I had a backlink sitting on. With that said please share opinions that are supportive if you disagree. BTW…indexkings.com I linked above is a free site, so maybe you can create a study for us only costing you time.
Final thought, if you receive a good backlink its likely a popular site and Google will find it without issue. If you paid for a link on some obscure site then sure indexing may be worth it?