Prototype — Open-source hardware in development
Bottle-mounted phone arm

How to mount your phone?
we are figuring it out...

Our team is working on a slim strap that clips to any standard bottle. A folding articulated arm unfolds to hold your phone — via MagSafe — for your training. The filled bottle is the counterweight. No tripod, no desk, no extra gear.

See how it works Open-source CAD

Everything you need is already in your hand.

Concept image of The Marlin bottle-mounted folding arm holding a phone at eye level

A concept image of how it would work — strap it to a filled bottle, unfold the arm, and your phone sits steady at eye level. No tripod required.

Design

Compact. Stable. Affordable.

Engineered for people who already carry a water bottle everywhere.

Universal bottle fit
A silicone-backed strap wraps around any standard 500 ml–1 L water bottle — Nalgene, Hydro Flask, CamelBak, plain plastic.
Articulated folding arm
Two hinged segments fold flat when not in use. Unfold and lock to position your phone anywhere from chest to eye level.
Counterweighted by design
Physics does the work. A filled bottle (400–700 g) counterbalances your phone with no additional weights or clamps needed.
MagSafe mount
Your phone snaps on magnetically — no clamps, no screws. Works with MagSafe iPhones and any phone with a magnetic ring case. Portrait or landscape in one twist.
Folds to pocket size
Collapsed flat, the arm adds less than 12 mm to the bottle's diameter. Slides into any gym bag side pocket.
No extra gear needed
The only hardware you need is your phone. No tripod, no external power, no Bluetooth shutter — just mount and press record.
Setup

Three steps. Under ten seconds.

From bag to filming before your warm-up is over.

1
Attach the strap
Loop the silicone strap around your water bottle and click the buckle. Works on any bottle from slim 500 ml to wide 1 L.
2
Unfold the arm
Swing the two segments out and lock each joint. Position the phone holder at the angle you want — portrait or landscape.
3
Snap on your phone
Your phone clicks onto the MagSafe mount. Set your bottle down on any flat surface — the water inside keeps everything steady.
Open Hardware

Print it yourself.

Spin the model below to see it deployed and folded. The design files will be open-source — print one on any home 3D printer.

Loading 3D model…
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CAD files on GitHub
The full open-source project — colored 3MF assemblies, print-ready STL/STEP exports, the parametric CadQuery source, and a bill of materials. Star it, print it, break it, tell us what happened.
View the repository
Get in touch
We're looking for funding and early users to make this shareable and far more accurate. For inquiries, collaboration, or early access, contact piranha@studioprajna.com.
Send an email

This is an early v0 prototype — expect the design to evolve. Watch the repo for updates.