You can get long range wifi stuff that will go far longer than 75 meters, but in my experience it is about a reliable as Wifi ever is. I have one of these on my shed back to a normal AP in the house
http://www.tp-link.com.au/products/d...L-WA7210N.html
It gets me basic connectivity to the shed (Around 100M from the house AP) but throughput while tests show about 25mb/sec is really unreliable, I use it for an intercom link and for media streaming and even music from the server in the house can be a challenge sometimes. Video seems to be buffered differently and is actually more reliable than music!
I am so heartily sick of Wifi that I just spent a day on an excavator to install a comms conduit to the shed to build a fibre optic link (No earthing issues that way) Now I just have to get the shovel out and install the P2 pit I bought for the pipe to give me a hauling point. Then a couple more bits of electronics to make it all work.