Africa’s recent communications ‘revolution’ has generated optimism that using mobile phones for health (mhealth) can help bridge healthcare gaps, particularly for rural, hard-to-reach populations. However, while scale-up of mhealth pilots remains limited, health-workers across the continent possess mobile phones. This article draws on interviews from Ghana and Malawi to ask whether/how health-workers are using their phones informally and with what consequences. Health-workers were found to use personal mobile phones for a wide range of purposes: obtaining help in emergencies; communicating with patients/colleagues; facilitating community-based care, patient monitoring and medication adherence; obtaining clinical advice/information and managing logistics. However, the costs were being borne by the health-workers themselves, particularly by those at the lower echelons, in rural communities, often on minimal stipends/salaries, who are required to ‘care’ even at substantial personal cost. Although there is significant potential for ‘informal mhealth’ to improve (rural) healthcare, there is a risk that the associated moral and political economies of care will reinforce existing socioeconomic and geographic inequalities.