EF vs Observe.
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
EF
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EF: ejection fraction, an iPhone and Apple Watch application, can calculate ejection fraction easily. Teichholz formula is used to calculate EF.
Observe.
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Observe, user-friendly app designed for healthcare professionals to assess heart failure with preserved ejection fraction, featuring the Heart Failure Association (HFA) of the European Society of Cardiology (ESC) scoring systems: HFA-PEFF and H2FPEF (U.S. Score) guidelines. A precise tool to calculate HFpEF risk score using functional, morphological, and biomarker data. It gives a probability and percentage estimation of HFpEF, aiding diagnosis. However, it's not a substitute for professional medical advice or diagnosis. Healthcare providers should rely on comprehensive medical evaluations and their expertise when interpreting results.
Screenshots
Verdict
The clearest difference is update cadence: Observe. at every 8 months against EF's every 48 months. EF's advantage is device support (4 vs 2). On price, ads, in-app purchases and iOS requirement 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
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
EF ships an update every 48 months, Observe. every 8 months. The most recent releases landed on October 1, 2026 and October 2, 2026 respectively.
| Parameter | EF | Observe. |
|---|---|---|
| Price | Free | Free |
| Update frequency | Every 48 months | Every 8 months — better |
| Ads | No | No |
| In-app purchases | No | No |
| Devices | iPhone, iPad, iPod, Apple Watch — better | iPhone, iPod |
| Requires iOS | 12.0 — better | 13.0 |
| Further details — not scored | ||
| Size | 22 MB | 29 MB |
| Age rating | 17+ | 4+ |
| Developer | Keiji Matsui | SELECT ICT Systems SAE |
In-app purchases
EF
No in-app purchases
Observe.
No in-app purchases
