At first blush, the teachings of exclusive nembutsu in Jodoshu would seem to fit this description.
However, as you rightly observe, it's not that simple.
Honen divided practices into "right" and "miscellaneous" practices. The "right" practices are "right" in that they directly pertain to birth in Amitahba's Pure Land. They are the practices found in the Three Pure Land Sutras: single-mindedly reading and reciting the Three Sutras, contemplating the "principal and dependent rewards in that land" (i.e. the adornments of the Pure Land), doing prostrations before Amitabha, reciting his name, and giving praise/offerings to Amitabha.
Of these, reciting his name (as buddha-remembrance) is further singled out as the "rightly established act" since it most intimately connects one to Amitabha through mind, speech, and body. It's also mentioned in Amitabha's 18th Vow. The other "right" practices are termed "auxiliary".
Honen's (and Shandao's) teaching of exclusive nembutsu is the emphasis on this rightly established act as best suited and most efficacious for bringing devotees to the Pure Land. However, the other right practices are obviously not amputated from Jodoshu and are taught in the sutras foundational to the school. A Jodoshu service performed at home includes incense offering, bows, recitation of sutra and often Honen's Single-sheet Document, and prayers and dedication of merit, in addition to the core of nembutsu.
The remaining practices, such as those of the Holy Gate, are termed "miscellaneous" since one must deliberately dedicate the merits to birth in the Pure Land. Otherwise, they have no direct connection to Amitabha.
In Honen's Senchakushu, he sums up the difference:
If we perform the rightly established and the auxiliary practices, our heart always remains intimately with and near to Amitabha, and we never cease to bear him in mind. Hence these are called uninterrupted. When we perform the other miscellaneous practices, however, our concentration [on Amitabha] is always liable to be broken. Even though we can be born [in the Pure Land] by dedicating the merit of such practices to that end, they are called estranged miscellaneous practices.
PorkChop could give more info on this.