Stablecoin-linked credit cards are emerging as a significant disruptor in the banking sector, allowing users to store, spend, and earn from stablecoins like USDC and USDT. These cards enable transactions at any Visa or Mastercard-accepting merchant by converting stablecoins to fiat at the point of sale. Ether.fi exemplifies this innovation with a model offering up to 10% yield on stablecoin holdings and borrowing at 4% interest. Despite their potential, these cards face challenges such as private key management, gas fees, and asset volatility. However, they represent a promising integration of decentralized finance (DeFi) with everyday financial activities, potentially becoming a 'killer app' in the financial technology landscape.