If [a] person [is] only mindful [of] Amitā[bha Buddha (i.e. Āmítuófó)], [this] is named [as the] unsurpassable, profound [and] wonderful meditation.
– Mahasamnipata (Great Collection) Sutra
To be mindful only of Amituofo means to practise wholehearted (single-minded) mindfulness of him. As the quote shows, mindfulness of Amituofo, be it via verbal or silent chanting is also a form of meditation, as it trains the mind to progress in calmness and clarity. The concentration (samadhi) attainable is supremely peaceful and blissful as it is supported by the Other-power of Amituofo too.
In fact, Buddha mindfulness is the supreme form of meditation, because it leads to birth in Pure Land, to be able to meet and learn from many Buddhas directly, and to always be with the best of spiritual friends in the best environment for spiritual training. Spiritual progress is thus swift and without backsliding, until supreme enlightenment is attained – for guiding more beings to the same supreme enlightenment.
Mindfulness of Buddha is also repeatedly taught by the Buddha in some 300 assemblies, as recorded in the sutras, as it is the safest and easiest path of practice, that leads to the most fruitful attainment. As stated in the Amitabha and Immeasurable Life Sutra, it is also a teaching praised by all Buddhas, that all Buddhas will teach.