Disk images tend to be large yet available disk space remains a scarce resource even in times of multi-terabyte devices. For this reason, it can still be handy to retrieve a disk image from the Internet and write it to a device without having to temporarily store it on your disk.
The below command will retrieve some.iso by means of wget and pipe the downloaded data to dd‘s stdin. The dd command will then write everything to the /dev/sdX device:
wget -q -O - http://example.com/some.iso | sudo dd of=/dev/sdX bs=4M
Be careful to supply the right output device file. As we all (should) know, any mistake in using dd can cause you erased devices and sleepless nights.