TipJar is currently running on the Ropsten testnet.
This decentralized application allows you to send ETH without knowing the wallet address of your recipient. Simply enter the amount in USD you want to send, click Generate Link, and send your desired recipient the resulting URL (privately)!
When you enter an amount and click Generate Link, the hash of a random alphanumeric string is produced client-side. This hash is then passed into TipJar's smart contract on the Ethereum network along with the amount of ETH you chose to send, where the hash is mapped to the amount. The alphanumeric string is contained in the generated link, and when your recipient opens the link and claims the tip, it is hashed and sent to the smart contract. The hash matches the one produced when you generated the link, so the amount of ETH mapped to it is transferred to your recipient.
The recipient of your link does not need to have ETH in their wallet to claim their tip. TipJar utilizes OpenZeppelin's GSN, so your recipient's gas fee is deducted from the amount you specified when generating the link to be used on their behalf when they claim it.