Short answer — best options by goal

• Best overall sleep + health ecosystem: Apple Watch (Series 9/Series 10 or Ultra). Best if you want a full smartwatch with reliable heart-rate, HRV, respiratory rate, sleep stages, ECG, and growing sleep-apnea notifications; integrates tightly with iPhone Health. (Apple.com)

• Best dedicated sleep ring (discreet + continuous overnight data): Oura Ring (Gen 3/Gen 4). Very detailed nightly sleep staging, HRV, temperature and readiness scores — small and comfortable for most sleepers (but note ongoing user reports about software/ battery variability and subscription). (wearablewellnessgear.com)

• Best for recovery/athletes (sleep + strain/recovery): WHOOP (strap). Focuses on sleep, recovery and strain with deep HRV and recovery coaching — subscription model and no on-device screen. Good if you want performance/strain-first insights. (techvireo.com)

• Best hybrid watch with clinical features (sleep apnea screening + long battery): Withings ScanWatch / ScanWatch 2. Hybrid look, good sleep staging, SpO2 and sleep apnea detection features in a watch form. (techvireo.com)

• Best for clinical-grade sleep (EEG/headband): Dreem (headband) or Muse S. These use EEG to measure brain activity for the deepest sleep staging and are useful if you have chronic insomnia or want clinical-grade overnight data and CBT-I programs. (techvireo.com)

• Best for affordable/basic tracking: Fitbit Sense 2 or more budget Fitbit models. Good sleep-stage tracking, SpO2 estimates, stress tools, and generally lower price; Fitbit Premium subscription unlocks advanced insights. (wearablewellnessgear.com)

• New/interesting niche option: Garmin Index Sleep Monitor (upper-arm band) — a dedicated overnight armband announced in 2025 that focuses exclusively on sleep with long battery life and detailed metrics if you dislike wrist wear while sleeping. (theverge.com)

Quick pros/cons summary (practical buying points)

• Apple Watch (Series 9/10, Ultra)

  • Pros: Rich sensor suite (HR, HRV, ECG, respiratory rate, wrist temp), sleep-apnea notifications, powerful app ecosystem and medical integrations. Great if you want an everyday smartwatch + sleep metrics. (Apple.com)
  • Cons: Shorter battery life than rings/straps (usually 1–2 days with heavy use), best experience on iPhone, can be less comfortable overnight for some.

• Oura Ring (Gen 3 / Gen 4)

  • Pros: Very comfortable at night, long-ish battery (varies by gen), continuous temp + HRV, strong readiness/sleep scoring. Discreet and minimal interference with sleep. (wearablewellnessgear.com)
  • Cons: Higher up-front cost plus subscription for full features; some users report occasional tracking or battery issues and customer-service complaints. (Reddit.com)

• WHOOP

  • Pros: Excellent for athletes — continuous strain and recovery scoring, sleep coaching. Small, lightweight, long measurement windows.
  • Cons: Subscription-only model; no display; focused on performance rather than general smartwatch features. (techvireo.com)

• Withings ScanWatch

  • Pros: Stylish hybrid, good battery life, SpO2 and sleep apnea detection, FDA/CE-backed features in some models/regions.
  • Cons: Less real-time interaction than smartwatches; not a full smartwatch OS. (techvireo.com)

• Dreem / Muse S (EEG headbands)

  • Pros: EEG gives the most accurate sleep-stage and sleep-onset data; some include guided CBT-I or neurofeedback to improve sleep.
  • Cons: Not wearable daytime; bulkier; more clinical and more expensive for some users. (techvireo.com)

• Fitbit Sense 2

  • Pros: Affordable, reliable sleep staging, stress tools, ECG/SpO2 estimates, broadly compatible across phones.
  • Cons: Advanced insights behind Fitbit Premium subscription; not as deep as EEG or specialized devices. (wearablewellnessgear.com)

How to choose (fast checklist)

• Want a daily smartwatch + sleep? → Apple Watch (if iPhone) or a Garmin/Withings hybrid.
• Want the least intrusive overnight device? → Smart ring (Oura) or upper-arm armband (Garmin Index).
• Are you an athlete tracking recovery/strain? → WHOOP or Garmin sports watches.
• Suspect medical issues (sleep apnea, arrhythmia)? → Look for devices with sleep-apnea screening/SpO2/ECG (Withings ScanWatch, Apple Watch with apnea notifications, clinical sleep study referral). These can screen but are not definitive diagnoses — see a clinician for testing. (Apple.com)
• Want clinical-grade sleep measurement? → EEG headband (Dreem, Muse).

Costs & subscriptions (typical)

• Smartwatches (Apple, Garmin, Withings): $200–$800+ one-time; some features free, some require a premium app subscription for advanced trends.
• Rings (Oura): ~$250–$400+ one-time, plus optional/required subscription for some analytics.
• WHOOP: Usually free/low-device cost but ongoing monthly/annual subscription.
• EEG headbands: $300–$600 with some programs requiring extra fees. (wearablewellnessgear.com)

Practical tips before buying

• Check night comfort: if you sleep on your side, wrist bulk can be uncomfortable — rings or armbands can be better.
• Battery life matters: if you won’t charge nightly, prefer rings/armbands/hybrid watches.
• Evaluate data use: do you want coaching/actionable suggestions (WHOOP, Fitbit Premium, Apple/Withings insights) or raw/clinical data (EEG, ScanWatch)?
• Privacy & subscription: read the vendor’s policy on data sharing and whether a subscription is required to access core features.
• For health concerns (apnea, arrhythmias): use wearables only as a screening tool and follow up with a healthcare provider or formal sleep study for diagnosis. (Apple.com)

If you want, I can:

• Recommend 2–3 specific models tailored to your budget, phone (iPhone vs Android), and sleep habits.
• Compare two models side-by-side (features, battery, price, subscriptions).

Would you like a short personalized shortlist (I can tailor to iPhone vs Android and budget)?