Yep, there are layer 2 solutions that can facilitate your wager with your friends without the need for everyone to download an app. One such solution is the Lightning Network, a second-layer protocol built on top of the Bitcoin blockchain. It enables fast and low-cost transactions.

For a progressive web app type of solution, you can explore custodial Lightning wallets like BlueWallet or Wallet of Satoshi. These wallets offer user-friendly interfaces accessible via web browsers, making it easier for your friends to participate in the wager without the hassle of app downloads.

With a Lightning wallet, you can create a shared payment channel with your friends, pool your wagers, and the winner can then collect their winnings efficiently and cost-effectively using the Lightning Network. Just ensure everyone involved is familiar with using Lightning wallets to avoid any confusion.