# Blood Oxygen App vs TrialLink

The clearest difference is in-app purchases: TrialLink at none against Blood Oxygen App's 14. TrialLink also leads on rating (5.0 vs 4.6). Blood Oxygen App's advantage is ratings volume (31K vs 4) and chart position (#32 vs unranked). On price, ads, device support and iOS requirement there is nothing between them.

Both are free to download. Blood Oxygen App sells 10 in-app purchases, starting at $2.99 per 7 days. TrialLink asks for nothing beyond the download.

TrialLink holds the better App Store score, 5.0 against 4.6. That said, the two scores are not equally well evidenced: Blood Oxygen App has 31K ratings behind it against 4, so its average is the more settled of the two.

Blood Oxygen App ships an update every 2 weeks, TrialLink every 5 weeks. The most recent releases landed on October 31, 2026 and October 15, 2026 respectively.

## The numbers

| Metric | Blood Oxygen App | TrialLink |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [4.6 (31K ratings)](https://appshunter.io/ios/app/blood-oxygen-app/id1541992656/reviews) | **[5.0 (4 ratings)](https://appshunter.io/ios/app/triallink/id6769185049/reviews)** |
| Number of ratings | **31K** | 4 |
| Positive reviews | 25.7% of reviews | — |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | **Every 2 weeks** | Every 5 weeks |
| Monetization | Freemium | **Free** |
| Best chart rank | **#32** | — |
| Size | 317 MB | 37 MB |
| Requires iOS | **15.0** | 15.1 |
| Devices | iPhone, iPod, Apple Watch | iPhone, iPad, iPod |
| Age rating | 12+ | 17+ |
| Developer | [AboutMe Apps, Inc.](https://appshunter.io/developer/1088980079) | [Kachina Health, LLC](https://appshunter.io/developer/1868224901) |

## What reviewers say

### Blood Oxygen App

[App page](https://appshunter.io/ios/app/blood-oxygen-app/id1541992656)

**Currently charting:** #32 Top Grossing · Medical (US App Store)

Monitor blood oxygen levels and heart rate using your phone's camera or by syncing with your Apple Watch. Track vital signs, share data with your doctor, and access curated health articles. Includes breathing exercises and sleep reports.

**Highlights:** Blood oxygen monitoring, Heart rate estimation via camera, Apple Watch sync, Data logging and export (PDF), Box breathing exercises, Sleep reports

**Features:** macOS Compatibility, Apple Watch app, Vision Pro support

**In-app purchases (10)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Premium features set | $2.99 | per 7 days |
| Pulse oximeter for Apple Watch | $9.99 | per month |
| Premium month | $9.99 | per month |
| Premium month | $12.99 | per month |
| Premium features (all) | $19.99 | per year |
| Premium | $19.99 | per year |
| Premium features set | $24.99 | per year |
| Premium features set | $24.99 | per year |
| Blood Oxygen＋Body Temperature | $29.99 | per year |
| Premium year | $39.99 | per year |

**What reviewers like**

- ⭐ Awesome app
- ⭐ Very easy to use
- ⭐ Helpful for monitoring health conditions
- ⭐ Detailed data logging

**What reviewers complain about**

- ❌ Doesn't accurately measure blood oxygen levels
- ❌ Requires premium subscription for key features
- ❌ Inconsistent and unreliable performance
- ❌ Deceptive marketing and false advertising
- ❌ No way to contact customer support

**Reported bugs**

- App crashes and freezes frequently
- Inaccurate heart rate and oxygen level readings
- Compatibility issues with certain Apple Watch models

**Requested features**

- Add audible/vibration alerts for low oxygen levels
- Improve automatic oxygen level monitoring
- Provide more control over reading frequency


### TrialLink

[App page](https://appshunter.io/ios/app/triallink/id6769185049)

This B2B SaaS platform streamlines clinical trial operations for sponsors and investigators. It provides secure, study-specific environments accessible only to authorized users via direct login credentials. Access is managed by sponsors, not through public sign-up.

**Highlights:** B2B SaaS platform, Clinical trial operations, Study-specific environments, Secure investigator access, Sponsor-managed access

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Blood Oxygen App free?

Blood Oxygen App is free to download, with in-app purchases available.

### Is TrialLink free?

TrialLink is free to download, with no in-app purchases.

### Which has better reviews, Blood Oxygen App or TrialLink?

TrialLink is rated higher. Blood Oxygen App averages 4.6 out of 5 from 31K ratings, while TrialLink averages 5.0 from 4 ratings.

### Do Blood Oxygen App or TrialLink have ads?

Neither Blood Oxygen App nor TrialLink shows ads.

### Which is updated more often, Blood Oxygen App or TrialLink?

Blood Oxygen App ships an update every 2 weeks, and TrialLink every 5 weeks. Most recently, Blood Oxygen App was updated on October 31, 2026 and TrialLink on October 15, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*