Hi Vivek,
I have gone through all the replies and trying to figure out what you want to achieve and it seems you want to trigger an email sequentially to all the approvers right?
I don't think currently anything standard is there so you have to design an ABAP workflow to achieve this via ppf action etc.
As far as design goes if you expect this in standard it should also be included in mobile apps but we know good things comes in small packages(SPs)
Regards
Prakhar