Database for live mobile tracking
I happen to work for an IoT\M2M company and we have been using SQL Server just fine for years...  Much of the architecture is all event\transaction driven and process based on an \time\event\status and have denormalized the data for multi-purpose uses.

Now, ideally when you experience the type of growth that we have over the last few years with millions of connected devices your problem becomes one of carrier relations and how are you going to get better rates and roaming agreements from your carriers...

GPRS, SMS, Data... It all cost's but I digress. Your going to want to store LAT\LONG in datatypes of FLOAT. I think GOOGLE does it with a length of FLOAT(10,6)?

MySQL or Postgres Spatial with GIS extensions is another option.

Good Luck!