Beside decreasing the abilities, individual difference prevails among older adults, as some individuals are completely healthy at the age 90 while some are not at even 60. In context of touchscreen interface design, it is critical to understand the design space as a function of abilities. In this work, we articulate a better understanding of the effects of ageing and examine their HCI task performing capabilities in terms of interfaces design. We design a text-entry interface in particular, as ageing users often achieve slow text entry performance, thus proving to be a bottleneck for technology use. Our developed text entry interface is tuned based on the parameter values for Elderly having finger tremor. We present initial study results showing the improvement of the accuracy of touch typing in smartphone over the baseline Qwerty keyboard. By carefully considering other sensorimotor abilities, we believe that the current smartphone text-entry interface designs will become more usable to the ageing populations.