That's not a "transaction accelerator";
You're just making sure someone's else transaction doesn't get dropped out from the mempool. Miners will still prefer to confirm transactions with a higher fee.
It is the name of Wordpress plugin
Description says: "Have low-fee transactions that have been unconfirmed for hours? We can speed up confirmation by rebroadcasting the transaction to the bitcoin network."
I don't know how it exactly work...