# ZOLL vs RTB2

The clearest difference is in-app purchases: ZOLL at none against RTB2's 1. ZOLL also leads on iOS requirement (13.0 vs 15.1). RTB2's advantage is update cadence (every 5 days vs every 17 months). On price, rating, ratings volume and ads there is nothing between them.

Both are free to download. RTB2 sells 1 in-app purchase, starting at $2.99 per month. ZOLL asks for nothing beyond the download.

On the App Store both sit at effectively the same score — 5.0 for ZOLL against 5.0 for RTB2. Both are backed by a comparable volume of ratings — 3 and 2 respectively.

ZOLL ships an update every 17 months, RTB2 every 5 days. The most recent releases landed on October 13, 2026 and September 26, 2026 respectively.

## The numbers

| Metric | ZOLL | RTB2 |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [5.0 (3 ratings)](https://appshunter.io/ios/app/zoll-messenger/id1604867248/reviews) | [5.0 (2 ratings)](https://appshunter.io/ios/app/rtb2-respiratory-reference/id6757658847/reviews) |
| Number of ratings | **3** | 2 |
| Positive reviews | — | 100.0% of reviews |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 17 months | **Every 5 days** |
| Monetization | **Free** | Freemium |
| Size | 2 MB | 46 MB |
| Requires iOS | **13.0** | 15.1 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPod |
| Age rating | 17+ | 4+ |
| Developer | [ZOLL Data Systems, Inc.](https://appshunter.io/developer/385812404) | [Bbytetechworks LLC](https://appshunter.io/developer/1844731958) |

## What reviewers say

### ZOLL

[App page](https://appshunter.io/ios/app/zoll-messenger/id1604867248)

This mobile application offers a streamlined way for healthcare professionals to access patient status and critical information directly on their smartphones. It provides actionable insights to support informed decision-making in medical settings.

**Highlights:** Patient status access, Patient information retrieval, Actionable insights, Mobile accessibility, Simplified interface

**In-app purchases:** none


### RTB2

[App page](https://appshunter.io/ios/app/rtb2-respiratory-reference/id6757658847)

This medical reference app provides respiratory therapists and students with essential clinical tools. It features ventilator mode guides, therapy calculators, and oxygen guidance in a clean, organized format for quick access in critical care settings.

**Highlights:** Ventilator mode reference guides, Respiratory therapy clinical calculators, Oxygen device guidance, Structured respiratory care information, Fast clinical review format, Advanced calculators (Pro)

**Features:** macOS Compatibility

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| RTB2 Pro | $2.99 | per month |


## Frequently asked questions

### Is ZOLL free?

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

### Is RTB2 free?

RTB2 is free to download, with in-app purchases available.

### Which has better reviews, ZOLL or RTB2?

ZOLL and RTB2 are both rated 5.0 out of 5 on the App Store, from 3 and 2 ratings respectively.

### Do ZOLL or RTB2 have ads?

Neither ZOLL nor RTB2 shows ads.

### Which is updated more often, ZOLL or RTB2?

ZOLL ships an update every 17 months, and RTB2 every 5 days. Most recently, ZOLL was updated on October 13, 2026 and RTB2 on September 26, 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.*