Use a logo that incorporates symbols normaly associated with subscribing buttons, an "S", and symbols associated with universality and cross-platform utilizatio

Use a logo that incorporates symbols normaly associated with subscribing buttons, an "S", and symbols associated with universality and cross-platform utilization. This will give you a springboard for incorporating your project's name, and illustrate that it's universal (a central point) along with showing its main purpose - subscribing. I would recommend something like an S with an infinity symbol overlaying the top curve of the S, and the lower curve curling into an arrow pointing down towards the bottom of the screen. Hope that helps :)