Hi,
I am Software Engineering Professional and I can implement this Android application for you.
This system should consist of Back end (Database and server) and Front end (Android Client) as you mentioned.
Back end (server and Database)
There should be database which consist of all the registered volunteers with their current location. (Current location can be updated with periods of half an hour.)
Apart from that there will be tables consisting past normal users (people who got help from this system) and active normal users(people seeking help via this system.)
Web Services
We can implement Webservices to register with system for volunteers, register for help (normal users), get active help seekers around some area
Android Client
Register interface for normal user, volunteer, interface to show help seekers around some area
According to my evaluation above is the main system components.
Apart from that we can implement push notifications based on SMS and Emails as well if you want.
Looking forward to hear from you.
Thank you.
Best Regards.
ROMANUWA