Nothing will ever best pumping a Dr. Beat through an amp for deep rhythmic exploration and practice, but the inconvenience of shouldering a 30-Watt-er to rehearsal every day is difficult to argue. Until recently, Frozen Ape's "Tempo Advanced" was the Spektral (iPhone) app of choice with its intuitive finger-swipe interface and not-unpleasant tick timbres. With the plethora of polyrhythms we've encountered in Thomas Adés' "Arcadiana" or Hans Thomalla's "Albumblatt" a standard metronome loses its efficacy.
Mining through the droves of metronome apps, I happened upon "Metronomics", a simple-looking program with one killer feature: customizable subdivisions. As a tear of joy rolled down my cheek (and the soundtrack swelled, etc.) I discovered that 1-100 beats per 1-100 subdivisions were now possible. Best educated guesses at how Eliza Brown's 15:4 lies in her "Quartet No. 1" are now a thing of the past. The real boon here is the ability to hear subdivisions against the prevailing beat as a composite, allowing the musician to get a global sense of each figure. Also, if the performer wants to determine how a particular subdivision falls in relation to the larger beat (extremely useful when working with a conductor), this clarifies the geography.
Of course, no app is perfect. Here, the beats are derived from percussion instruments, which can be distracting when spending hours at a score, disassembling complex passages. I'll look forward to developer John Nastos offering a wider array of sonic choices in the future, but for the moment, I'm in love.