Is there an API / service for uploading assets from a web app?

Question

I'm curious if a service exists that handles file uploads and provides a UI widget.

Ideally it would work as such:

1. They provide an embeddable and customizable file upload widget (upload progress, multiple files) with good cross browser / device compatibility.

2. The upload widget detects file types and provides an optional UI for resizing / cropping images, videos, tagging documents, etc.

3. Files get uploaded to their service (reducing load on my app server) and get stored on their file system (or their S3 account etc).

4. After upload - the file's URL is returned to my app to be stored locally.

Googling hasn't produced anything promising, but I feel that someone must have built this by now.

Answer 1

To answer my own question:

http://transloadit.com