Until quite recently I used to be an empty-mind meditation fundie who would have curtly replied to this thread: "All you need is a timer, meditation apps are for daydreaming junkies and sissies!" I even started this
thread on music and meditation in which I voiced my disapproval for music as a temptation to merely drift off and space out, i.e. not meditating at all (in the strictest zazen sense of the word). Additionally, I had planned to open another one asking for a discussion regarding the difference between meditation and trance which is anything but clearcut, and I might still do that.
Now I rather think that you'll have to draw the dividing line according to other criteria. On the one hand, you have austere religious practices e.g. within the context of Buddhism, with very long-term goals, leaving no leeway for experimentation whatsoever, and on the other… let's call it free-form mental journeying as well as possibly pathworking. I'm so prejudiced against the latter that I have to try really hard not to wax polemical against it. There was a stage in my meditation practice when I was struggling to banish certain songs from my mind - imagine sitting in a quiet room while guitar power chords and thrashing cymbals were raging in your head. Things have much improved since then but these songs will still make an appearance now and then. To imagine that those apps will not only play hypnotizing music lulling me into a (superficial? temporary?) state of well-being while some voice commands me what to do, what to think and imagine… a nightmarish idea for me who strives to make his mind a complete blank as instructed in Caroll's Liber MMM and Bardon's
IIH Step 1
.
In a book about Buddhism, the author recounts that a woman once came to his teacher and wished to learn meditation, so he taught her the basics and send her home. One day she returned and complained that all she could find in her mind were knots of anxiety and unease. "Good", the teacher said, "you're learning awareness." She replied, "I don't care about awareness, I want peace." Which is exactly the point. Nobody should be forced to walk an arduous path they didn't choose themselves on their own volition. A meditation app would have been probably better suited to her needs.
Another objection of mine is that guided meditations are artificially inducing emotions - so does music, so do movies, and it's the reason why we enjoy them but my aim is
equanimity, not indulging in all kinds of strange or exciting feelings (my mind still seems to have other ideas sometimes but anyway), and I don't mean fake Zen master tranquility but genuine calm from deep down once my addiction to emotional highs of any kind has died a natural death.
Without having tried one myself, I think that the purpose of meditation apps is producing all sorts of interesting experiences you're probably unable to kindle without their help. To be honest, I just don't like the idea, I'm puritan that way, but to each his or her own.