# 記石 vs ChironMotion IMU

記石 and ChironMotion IMU are too close to call on the numbers: across 6 compared parameters — price, update cadence, ads and in-app purchases among them — neither pulls far enough ahead to decide it. What separates them is feature set and interface, not measurable difference.

Both are free to download. 記石 sells 2 in-app purchases, starting at $0.99 per month and ChironMotion IMU sells 2 in-app purchases, starting at $3.99 per month. Whichever you choose, the download price is not the number that matters.

Both ship on a similar rhythm, roughly every 2 months. The most recent releases landed on September 10, 2026 and September 12, 2026 respectively.

## The numbers

| Metric | 記石 | ChironMotion IMU |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | Every 2 months | Every 2 months |
| Size | 4 MB | 25 MB |
| Requires iOS | **17.0** | 18.0 |
| Devices | iPhone, Apple Watch | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [HAO Yuan Cheng Cheng](https://appshunter.io/developer/1625456139) | [Yi-Fu Chen](https://appshunter.io/developer/1873701789) |

## What reviewers say

### 記石

[App page](https://appshunter.io/ios/app/id6465749193)

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| 月票 | $0.99 | per month |
| 套票 - 100條路線紀錄 | $0.99 | one-time |


### ChironMotion IMU

[App page](https://appshunter.io/ios/app/chironmotion-imu/id6758951844)

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Pro Monthly Plan | $3.99 | per month |
| Pro Yearly Plan | $39.99 | per year |


## Frequently asked questions

### Is 記石 free?

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

### Is ChironMotion IMU free?

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

### Do 記石 or ChironMotion IMU have ads?

Neither 記石 nor ChironMotion IMU shows ads.

### Which is updated more often, 記石 or ChironMotion IMU?

記石 ships an update every 2 months, and ChironMotion IMU every 2 months. Most recently, 記石 was updated on September 10, 2026 and ChironMotion IMU on September 12, 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.*