A service that let your customers use your DApp for free setting your wallet as the fee payer of your customer's transactions. Why this service exist if the transactions on Solana are so low? If we want to make mass adoption a reality, we need to implement some freemium models on our DApps, but we all know that, obviously, when a user create a wallet, he has ZERO money on it, so how could a user sign a transaction with no money at all? A service like Cowsigner is probably needed. You can stop reading here, but there are other use cases where you'd want to be the fee payer of your customer's transactions. For example: