I need help on designing a handheld storage based on micro SD Card + QSPI interface + Wi-Fi data transfer

iPhone users are very rich.

Their phones do not have SD Card slots.  They pay big money every month to icloud for storage.

USB sticks might be regarded as low class by them.  So,a separate high class portable storage fit their taste.  They take video along their trips and my device inside their pocket or bag stores their video through wifi (streaming whenever possible). 

Once the current SD Card is full, my app will alert the user to place an empty SD Card into my device.

Nowadays, SD Card can be up to 1TB.  So my device is a complete replacement of the icloud digital monopoly.

As my customer have more and more digital video collection, what he have to do is to keep them well indoor.  So, it is his own responsibility.

In the icloud digital monopoly scenario, if one does not pay a single month fee, all his digital creation will be locked.  If the subscriber bankrupts, Apple won't care about him.  It is a total loss from the icloud subscriber's viewpoint.

HKPhysicist said:

They pay big money every month to icloud for storage.

I am sure there will be market for iPhone users (or even Android users who have support for Magsafe accessories ) who wants a high class completely wireless storage setup. The current Magsafe SSD model still use USB C port for data transmission.

iPhone users are very rich.

Their phones do not have SD Card slots.  They pay big money every month to icloud for storage.

USB sticks might be regarded as low class by them.  So,a separate high class portable storage fit their taste.  They take video along their trips and my device inside their pocket or bag stores their video through wifi.

Very nice scenario.  

I interpreted as some kind of 'mesh node storage with failover redundancy' allowing you to add/remove to it. Almost like a RAID, but your ability to take away an individual node and it serve up the data as an individual computer itself.

 HKPhysicist this is an interesting endeavor to be sure but I am wondering if you can go into more detail on the use case.  For instance, what kind of data will you be transferring from the phone?  Also, how does the data get onto the phone in the first place?

Also explain your last sentence:

"Then, stack them up one by one infinitely under your desk."

Hey HKPhysicist ,

What exactly are you envisaging?

It's not entirely clear, is it that you're wanting to say, set down your phone after a busy day, and it auto synchronises to a device that's sat under your desk with shared storage?

I'm partly reminded of the old Eye-fi cards.

What's wrong with a USB stick. Less likely to get damaged, lost and it's at a similar price to SD card... www.sandisk.com/.../sandisk-ultra-usb-3-0

Yes, I tested it together on my PC and phone.  128MB took many minutes to transfer.

I need wifi for that purpose.

Transferring files through bluetooth is super slow. You can use it for files less than 2MB. 

I think your design should include some security requirements. Security bolted on later never seems to be as effective.