Comparison

Worry Monster vs REM Sleep Tracker

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Worry Monster

This app helps users manage worries and anxieties by providing a digital space to write down troubles. Once written, the app metaphorically 'eats' these worries, offering a sense of relief. All entered text is securely destroyed, with no data collection.

Highlights
  • Write down worries
  • Digital worry eating
  • Secure data destruction
  • No data collection
  • Mindfulness tool
Features
Read full description

Worry Monster help you deal with worries, troubles and woes. Write them down and let Worry Monster eat your worries away! It can chew a lot troubles and still smile on! All texts you write are destroyed by Worry Monster. We do not collect any data.

About

REM Sleep Tracker

This app analyzes Apple Watch sensor data to provide a sleep quality score. It offers detailed insights into sleep stages, heart rate, and weekly trends, helping users understand and improve their rest habits.

Highlights
  • Sleep quality scoring
  • Detailed sleep stage analysis (light, deep, REM)
  • Heart rate monitoring
  • Weekly trend tracking
  • Sleep bank concept for habit analysis
  • Apple Health integration
Features
Read full description

Sleep Monitor is the perfect app for people eager to enhance the quality of their nighttime rest. Thanks to an advanced algorithm, Sleep Monitor processes the data gathered by your Apple Watch sensors to provide you with an overall score representing the quality of your sleep. This innovative app offers a detailed analysis of the different sleep stages, monitoring light, deep, and REM sleep cycles, and providing information about your heart rate throughout the night. Additionally, Sleep Monitor allows you to track your progress with the "sleep bank" concept, a repository of your rest data that helps you better understand your habits and identify any issues. With Sleep Monitor, you can also monitor the weekly trends of various parameters, such as sleep duration, rest quality, and time spent in each sleep stage. This valuable information will enable you to make targeted lifestyle changes to improve your nighttime rest. Don't miss the opportunity to transform your Apple Watch into a powerful tool for better sleep and waking up more rejuvenated each day. Sleep Monitor is the ideal app for those seeking an ally in sleep management, with an intuitive design and a rich array of features. Download Sleep Monitor today and begin your journey towards more restful and regenerative sleep. Maximize the potential of your Apple Watch and discover how quality rest can improve your daily life! HealthKit Integrated with Apple Health for sleep stages, heart rate, respiratory frequency, age and gender data to calculate sleep quality. Sleep Monitor Premium Sleep Monitor offers a Premium version available as an auto-renewable subscription. Payment will be charged to iTunes Account at confirmation of purchase. Subscriptions automatically renew unless auto-renew is turned off at least 24-hours before the end of the current period. Account will be charged for renewal within 24-hours prior to the end of the current period at the rate of your selected plan above. Subscriptions may be managed by the user and auto-renewal may be turned off by going to the user's Account Settings on the device. Once purchased, refunds will not be provided for any unused portion of the term. Privacy policy: http://app.sleepscoreapp.com/Home/Privacy Terms of use: http://app.sleepscoreapp.com/Home/Terms

Screenshots

Worry Monster3 screens
REM Sleep Tracker4 screens

Verdict

The call

The clearest difference is price: REM Sleep Tracker at Free against Worry Monster's $0.99. REM Sleep Tracker also leads on update cadence (every 2 weeks vs every 27 months). Worry Monster's advantage is in-app purchases (none vs 2) and device support (3 vs 1). On review sentiment and ads there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

REM Sleep Tracker is free to download; Worry Monster costs $0.99 up front. REM Sleep Tracker sells 2 in-app purchases, starting at $9.99 per year. Worry Monster asks for nothing beyond the download.

UpkeepUpdate frequency

Worry Monster ships an update every 27 months, REM Sleep Tracker every 2 weeks. Both last shipped on October 24, 2026.

Scorecard6 real differences · 4 level
Worry Monster versus REM Sleep Tracker: the parameters behind the verdict, then further details
ParameterWorry MonsterREM Sleep Tracker
Price$0.99Free — better
Rating—4.2 (49 ratings) — better
Positive reviews0.0% of reviews0.0% of reviews
Number of ratings—49 — better
Update frequencyEvery 27 monthsEvery 2 weeks — better
AdsNoNo
In-app purchasesNo — betterYes
MonetizationPaidFreemium — better
DevicesiPhone, iPad, iPod — betteriPhone
Requires iOS14.0 — better16.0
Further details — not scored
Size3 MB25 MB
Age rating4+4+
DeveloperVille KangasNicola Eusebi

Customer experience

Worry Monster

Written reviews1 reviews
Positive0.0%
Neutral100.0%
Negative0.0%

REM Sleep Tracker

All ratings49 ratings
Positive79.6%
Neutral6.1%
Negative14.3%
Written reviews1 reviews
Positive0.0%
Neutral100.0%
Negative0.0%

In-app purchases

None

Worry Monster

No in-app purchases

2 purchases

REM Sleep Tracker

Subscriptions2
  • Sleep Score Premium Yearly$9.991 Year
  • Sleep Score Premium Yearly7 Days trial$29.991 Year

Questions

Is Worry Monster free?
Worry Monster costs $0.99, with no in-app purchases.
Is REM Sleep Tracker free?
REM Sleep Tracker is free to download, with in-app purchases available.
Do Worry Monster or REM Sleep Tracker have ads?
Neither Worry Monster nor REM Sleep Tracker shows ads.
Which is updated more often, Worry Monster or REM Sleep Tracker?
Worry Monster ships an update every 27 months, and REM Sleep Tracker every 2 weeks. Most recently, Worry Monster was updated on October 24, 2026 and REM Sleep Tracker on October 24, 2026.

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