Are there any cross-platform app frameworks that handle battery-efficient data transmission from wearables?

Yes. A few cross-platform app frameworks can help you build wearable-connected apps, but the battery-efficient data transmission part is usually handled by the wearable communication SDKs / platform APIs, not the UI framework itself.

Good options

1. Flutter

• Cross-platform for iOS, Android, web, desktop.
• Commonly used with:
  • BLE plugins for wearable/device communication
  • Platform channels for native HealthKit / Google Fit / Wear OS APIs
• Good if you want one UI codebase, but you’ll likely still need native work for the most battery-sensitive syncing logic.

2. React Native

• Cross-platform for iOS and Android.
• Works with:
  • BLE libraries
  • Native modules for Apple Watch / Wear OS integrations
• Similar to Flutter: solid for app UI, but efficient transmission depends on native code and the underlying device APIs.

3. .NET MAUI

• Cross-platform for mobile and desktop.
• Can use native bindings and BLE libraries.
• Better if you’re already in the Microsoft ecosystem.

4. Kotlin Multiplatform (KMP)

• Not a full UI framework by itself, but great for sharing logic across platforms.
• Useful for putting sync logic, batching, retry policies, compression, and power-aware state management into shared code.
• Often paired with native iOS/Android UI layers.

5. Capacitor / Ionic

• Cross-platform app shell with web tech.
• Can access native BLE and device features via plugins.
• Usually less ideal for highly battery-optimized wearable communication than Flutter/React Native/native implementations.

What really matters for battery efficiency

For wearable data transmission, battery efficiency usually comes from:

• Bluetooth Low Energy (BLE)
• Batching data instead of frequent tiny sends
• Adaptive sync intervals
• Event-driven updates rather than polling
• Compression / payload minimization
• Using platform-specific background transfer APIs
• Avoiding constant high-power connections

Platform-specific APIs to look at

If you’re targeting wearables, these are often more important than the framework:

• Android / Wear OS: Wearable Data Layer API, BLE, WorkManager, companion device APIs
• iOS / watchOS: HealthKit, WatchConnectivity, CoreBluetooth, BackgroundTasks

Practical recommendation

• If you want one codebase for the app UI: Flutter is often a strong choice.
• If you want maximum control over power-efficient syncing: use native wearable APIs, possibly with Kotlin Multiplatform for shared business logic.
• If you need BLE-based wearable integration, choose a framework with a mature BLE ecosystem and expect some native code.

If you want, I can also give you:

1. a framework-by-framework comparison table, or
2. recommendations based on Apple Watch vs Wear OS vs generic BLE wearables.