Jonbouy
I've used some things that offer a tap to tempo from the keyboard but because they are linked to the playback tempo and use the computer keyboard I've never had much success with them.
This though is simple and works like a charm I can see myself using it often, and the plus side due to the fact it isn't built into a DAW it works with whatever DAW I happen to be using at the time.
Until a couple of hours ago, I didn't think this capability existed in any DAW. This morning I was reading through some old issues of SoundOnSound, checking out the Cubase column. I came across one installment talking about tempo and a function called "Merge Tempo From Tapping". The "taps" in this case are MIDI note events, not mouse clicks, and according to the documentation you can select the duration: 1/2 notes, 1/4 notes, "etc.". What does "etc." mean? The documentation doesn't say if it allows eighth notes or tuples of any kind (there's not even a picture of the dialog box that comes up when invoking the function). In fact, this feature occupies only a meager half page in the manual. The main purpose seems to be to allow matching previously recorded audio to a tempo track, but presumably you could use it to "conduct" to a track you hear in your mind that you want to apply to quantized or step entered MIDI.
The fact that so little attention is paid to this in the manual sort of hints at how little importance most DAW designers relegate to this function. There is no discussion, for example, of whether or not you can use this feature to define a tempo track for a limited range of measures in a piece or how to start the tempo mapping at other than the beginning of a piece.
Nevertheless, this appears at first glance to be very much along the lines of the solution I arrived at ... a bit of experimentation is in order to see what's really there. But it does look close. I dearly wish that Cakewalk would take a close look and use Cubase as a guideline in determining how SONAR could (should!) be modernized tempo-wise.