Here comes a simple yet great cydia tweak from which you can make your very own pop-up notifications in iPhone, iPad or iPod Touch. Makemypopup is the name and it is available on Cydia for free.
Go to Settings >> Makemypopup to customize your notifications. Make sure Enabled switch is set to is on, fill in the title and Text field,
Now hold down the power button for couple of seconds to bring up your customized notification.
Press ok to dismiss. When not in use, disable it as it will an interference when you try to power off your device.