Cisco :: Monitoring 3g Data Usage On 887?

Have a problem coming my way with regards monitoring 3g data usage on an 887 router. The router will carry two links - x1 primary over the serial port and x1 secondary failover link utilizing 3g.
 
The 3g sim has an allowance of 1Gb per month (traffic has been baselined and this seems sufficient - not by me though).I have a requirement to monitor the 3g link and trigger an alert at say the 60% mark (600Mb).  Whatever mechanism is used to count the data also has to reset to 0 at the beginning of every month as data stats will be included in monthly reports. 
 
Second conundrum, I also have to somehow split out the data usage stats to show my customers usage as well as my own.  My own being management traffic (mainly snmp and icmp) and present this in the monthly report.
 
#1 - Does the 887 have some form of 3g accounting capability either via gui or cli that can fulfil my requirements above?
 
#2 - With splitting the data usage stats, could this be achieved using netflow and if it was possible, could i only have my flows sent down the Primary link (obviously only when it is active) and if the box fails to 3g have netflow just count the data until the Primary kicks in again.If no built in features can give me what i want i my go down the eem scripting route burt this is a last resort.