There are some software solutions as well as vocal performers. Anyway, it is unclear if vocal performer can produce any effect which would be impossible to get using software (if it modifies sound in certain algorithm, why can't be the same done in software?). Also, does it make any sense to use a combination of voice-modifying software and a vocal performer? What are the main recommendations for both software and vocal performers (if it makes any sense at all to use the latter in order to change voice from male to female)?
This is a great question that has several answers that are rather subjective, but I will give it my two cents in case you weren't aware of these options.
You absolutely can utilize a piece of hardware that specifically has "gender" settings on it, as well as much more. A common one a lot of folks get to do this is a VoiceLive Play, they aren't super expensive and do what they are made to do pretty well. By the time you add appropriate eq'ing, compression, and reverb on the audio clip - you can't even really tell it was made from the unit.
To be honest - you probably can do anything with a VLP(or the Boss unit you linked) in software with effects, filters(sidenote: check out some of the Fabfilter stuff if you are interested in software filters), vst's - but that just depends on how much time you have to do all the fx + processing.
Personally I find it easier to use the VLP, as it allows me to get closer to the sound I want from the start.
It could be as simple as transposing the recorded audio clip in your DAW, though with warping, it can slow down or increase the speed of the audio clip. Also, most DAW's even have a function in which you can utilize a single sample Sampler that allows you to draw midi notes that will play the sample on key. Sometimes this works really well, sometimes it does not.
There's also the Trax V3 VST VST plugin I keep hearing about. I personally haven't used it, but it's talked about a lot within my circle(trance and techno producers mostly).
The realm of producing vocals is very, very complicated, and takes lots of practice/experience.
Perhaps someone with a bit more experience than myself could add to this, but all of this is from my own experiences of working in the studio. Hope this helps.
First, you have to think of the sound you really want to achieve. Generally, female vocals are pitched higher than male vocals, so with some other processing you should be able to get what you want. But for live instant situations you'll need a real-time pitch manipulator software. I use image line's pitcher. It does real-time pitch manipulation and gender based formant shifting.
To go from a male to female voice you mainly want the pitch to be higher. That can easily be achieved by using an effect called pitch shift.
Pitch shifting effects are available stand-alone or as a part of multi-effects processors. They can be found as software (most DAW's have this effect available: REAPER, Logic, Cubase, .. or you can use a separate plug-in in VST or AU format) and as hardware (rack format, guitar pedal or other floor model formats, ..).