Gambal is a tiny transparent window that provides an overview of network, CPU and memory usages.
It's light-weight and uses libX11 for GUI and should work on all distros.
mouse wheel up/down changes transparency.
There are .deb and .rpm packages for different atchitectures in latest release page.
If you are on Arch linux and xorg-fonts-misc package is not installed. install it and logout and login to your desktop.
sudo apt-get install build-essential cmake libx11-dev
git clone https://github.com/ashtum/gambal.git
cd gambal
mkdir build
cd build
cmake ..
sudo make install
sudo gtk-update-icon-cache /usr/share/icons/hicolor