Since a live application will be the most simple example we can find in the wild then we can start there. The best live setup for a guitarist would be: Guitar > Amp. Most basic guitar practice amps come standard with on-board effects. The most common and basic effect options for these amps are clean and gain channels, reverberation and equalizer/tone settings. Some mid level amps will even add additional effect options like chorus and delay. In a live scenario this is usually enough to emulate a previously released recording of a processed guitar signal. In this scenario processing all of your guitar effects at the pre-amp stage inside of the amplifier is a suitable solution. The processed guitar signal is then captured at the speaker cone of the amplifier and then sent to the audio engineer. This is the basic and old school way of processing and amplifying a live guitar signal.
In the studio environment you have a little more time to set things up and you might want to save all of the effect processing chain settings for later use. Some amplifiers have memory storage for settings and can quickly be changed on the fly during a live performance. In the studio you can process your guitar signal at the amp and then capture the signal with a microphone to be sent to the engineer so that it may be recorded. Alternatively you can send a dry guitar signal to the engineer and use on board effects processing applications within the engineer’s digital audio workstation. These settings can also be saved for later use. This is a more recent technique used commonly in recording studios but there is still more technology being developed and that is where we move to next.
Today there are applications that can run on your phone or hand held computer device. You can literally have the power of an expensive recording studio packed into a iPad clone. Plug your guitar in and you have access to all of the magic that the engineer has. Applications that are available now include amplifier and cabinet emulators, dozens of effects and frequency enhancing tools and enough signal processing power to render the processed audio in almost real time (ASIO sound cards can render in under 1 ms).
If you have your effects processing chains spread out over several different systems it might be time to consolidate everything down to one system. Some features are brand specific but you can still get the settings close across all brands with common effects. Very soon a guitarist will be able to walk onstage with his guitar and his phone and stream his performance over a wireless network to the engineer. All of his processing and output signal in one place. Imagine setting your touch pad on the music stand and going to work while the pad gets charged.