i want responsive images for all my (multisite) wordpress

hello,

i want responsive images for all my (multisite) wordpress websites.

I found this:

https://premium.wpmudev.org/blog/diy-truly-responsive-images-on-your-wordpress-website/

but it seems very much work and certainly not an automatic solution?

Is there any new/better solution? what about this:

http://codecanyon.net/item/responsive-images-generator-loader/4663723

Another thing is about optimising wordpress for speed, what do you recommend? I found:

http://wordpress.org/plugins/google-pagespeed-insights/

Any other solutions part of your stack?

Looking forward to your reply.