Nerva

Local-first heart-rate overlay

Make your audience feel what you feel.

Your live BPM and stress, on stream as an overlay. Direct BLE, no cloud, no latency.

  • No credit card Start the trial without a payment method.
  • No account Install, see your BPM. No sign-up form, no email required.
  • 30-day refund Refund window opens after the trial, 60 days from install to decide.
  • Local data Your heart-rate signal never leaves your machine.

They emit over BLE

  • Garmin
  • Polar
  • COROS
  • Amazfit
  • Wear OS (via Heart for Bluetooth)
Is your watch supported? →

Built for any stream where the body reacts

Same product. Different stories.

  • Horror / reaction

    See if they actually flinch.

    Jump scare hits, BPM spikes. Your viewers see what your stomach did.

  • Ranked (FPS / LoL)

    Their cardio on the teamfight.

    1v3 clutch, last round. Your cardio tells the story your face hides.

  • Fitness / IRL

    Effort, made visible.

    Cardio is the workout. Show it where it belongs, native legitimacy.

  • Podcast / variety

    Tense moments, made visible.

    Tense interview moments become visible without being dramatized.

Why Nerva

What an overlay should be, and rarely is.

  • Zero latency

    Direct BLE → overlay. No cloud round-trip, no jitter on a peak heart-rate spike.

  • Zero cloud

    Your data never leaves your machine. No third-party broker between your strap and your stream.

  • Open overlays

    Bundled overlays are HTML/CSS. Edit the styles, build your own, or commission a custom one.

  • < 10 MB RAM

    Runs in the background, your PC won't feel it, even mid-stream.

Open overlays

Pick one. Edit the code. Or write your own.

Bundled overlays are HTML/CSS/JS folders. Tweak styles, consume the live CSS variables, package as .nerva-overlay. 

.heart {
  /* pulse with the live BPM */
  animation: pulse calc(60s / var(--nerva-bpm))
             ease-in-out infinite;
}

.bpm-num::after {
  content: counter(bpm);
  counter-reset: bpm var(--nerva-bpm);
}

.stress-fill {
  width: var(--nerva-stress-pct);
}
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Dev docs, build your own

Need a unique overlay for your brand? Commission a custom overlay →

Compatibility

Your watch probably already works.

Anything that broadcasts the standard BLE Heart Rate Service (UUID 0x180D). No proprietary hardware, no closed ecosystem.

Watches

Recommended for the vast majority of streamers.

  • Garmin, works out of the box
  • Polar watches (Ignite, Vantage, Grit X, Pacer)
  • COROS (Pace, Apex, Vertix, Kiprun 900)
  • Amazfit Zepp OS 3.0+ (T-Rex 3, Balance, GTR 4, Active 2)
  • Wear OS via Heart for Bluetooth (Pixel Watch, TicWatch)

Chest straps

For advanced HRV (RMSSD, SDNN, calibrated stress index).

  • Polar H10, reference sensor
  • Any chest strap on the BLE Heart Rate Service standard

Apple Watch and Samsung Galaxy Watch aren't recommended today, see why.

Pricing

One month free. Then 7.50 €/mo, billed yearly.

No credit card to start. No account to sign up. Cancel anytime, refund window stays open for 30 days after the trial ends.

  • Free trial
    0 € / 1 month

    Full Pro for one month. No card. No account.

    • Every feature unlocked
    • CSV / JSON export
    • Optional session highlight recording
    Download Nerva
  • Best value Pro · Annual
    7.50 € / month

    Billed 90 € yearly · save 30 €. Cancel anytime.

    • Keeps Nerva on this machine
    • All future updates included
    Choose annual
  • Pro · Monthly
    10 € / month

    Billed monthly. Cancel anytime.

    • Keeps Nerva on this machine
    • All future updates included
    Start monthly

Need a one-of-a-kind look? Commission a custom theme.

FAQ

Common questions.

What happens after the 1-month trial?

Hard cutoff at day 30, no degraded mode, no watermark. Reminders ship at D-7, D-3, D-1, D-0 so nothing surprises you. The refund window stays open for 30 days after the trial, so you have 60 days from install to decide.

Apple Watch and Galaxy Watch?

Apple Watch is not supported, it doesn't broadcast BLE heart rate. Samsung Galaxy Watch can connect through Heart for Bluetooth but the connection is unstable; we don't recommend it. A standard chest strap or a Garmin / Polar / COROS watch is the reliable path.

How does it compare to Pulsoid?

Pulsoid routes your heart rate through the cloud. Nerva goes BLE → overlay locally, no round-trip, no latency, no third-party broker between your strap and your stream.

Twitch, YouTube, or Kick?

All of them. The overlay is a local browser source you drop into OBS or Streamlabs. Platform-agnostic by design.

Mac or Linux?

Native builds for Windows 10+, macOS 12+ (Apple Silicon), and Linux (AppImage and .deb). Intel Mac is not supported today.

Try Nerva for one month, free.

Install, pair, drop the overlay into OBS. If it's not what you expected, walk away, nothing to cancel.

Download for Windows Download for macOS Download for Linux

Other formats: Linux .deb · macOS .app.tar.gz