Forget about using just a mic and running your electro straight into the PA; all-in-one effects units give acoustic-playing singer-songwriters more control over their sound.
TC-Helicon's Play Acoustic targets acoustic guitar and vocal in a single pedal, and Boss is doing likewise with the VE-8 Acoustic Singer, which boasts separate effect sections for voice and guitar, and throws in a looper for good measure.
Three footswitches control the action - the first operates a chorus effect for guitar but can also mute the signal and call up a tuner when pressed and held; the second turns vocal harmonies on and off but can also bypass all the vocal effects with a press/hold (useful for between-song patter); the third controls all the looper functions.
You can use the VE-8 in 'Stomp' mode, where the sound is set by the position of the knobs, but there are also 50 onboard memory slots to save whole setups, maybe one for each song, and these can be instantly recalled by holding down the first two footswitches simultaneously, then using them to scroll and recall patches.
For your guitar sound, you get reverb and a separate effect - nominally chorus, but you also get tremolo, delay, phaser and more - which sound as good as some individual stompboxes.
There's also an Acoustic Resonance knob that endows piezo pickups with more of the natural flavour of a mic'd-up guitar, and does a good job of limiting that piezo 'quack'. Particularly handy is a notch filter, which zeros in on any frequency that's causing feedback and reduces it very effectively.
Vocals get a similarly impressive spread, including an Enhance effect, which improves clarity with what sounds like a combination of compression and EQ, plus you can also switch in chromatic pitch correction to keep, ahem, wayward vocals more in tune.
The footswitchable effects can totally transform the voice, too - there's an AutoTune-style effect, robot-voice distortion and a radio voice. More tastefully, you get doubling or five different harmony types. These track your guitar playing rather nicely, changing with each chord, or otherwise can be set to a specific key.
The looper's similarly well-integrated, with 80 seconds of recording time and the ability to loop guitar and vocals independently. If your looping needs are simple and you don't need an undo function for the last overdub layer, it could even take the place of a dedicated pedal.
Even for effects novices, the VE-8 is intuitive and easy to use straight out of the box. At around £60 more than TC's Play Acoustic at street prices, the VE-8 has a similar feature set but very different ergonomics, giving it greater appeal for those who like instant hands-on control and want constant access to a looper via a dedicated footswitch.