Depends on your hardware manufacturer. Dell for example has a utility Flash64W.exe to apply a BIOS update from within Windows. Command line is
Flash64W.exe /b=".\TheBIOSUpdate.exe" /s /noReboot /l=%TEMP%\BIOSupdate.log
Currently we have this integrated as part of OSIM process via batch file. The batch file uses WMIC to determine model during WinPE phase then applies BIOS updates in a loop based on model generations (Optiplex D7 family have 7 BIOS options). The Dell utility is smart in that it won't downgrade your BIOS or apply incompatible BIOS with CLI options from above. So in theory could have directory of all the standard BIOS versions and have batch file that tries to apply them all in a loop, only applicable BIOS updates will apply.
With DSM queries and dynamic groups you could get more granular by querying BIOS version and IDing everything at/above your BIOS standard baseline with LIKE condition on your BIOS query (i.e... General Inventory.System Bios.Version LIKE '1.7.[5-9]'). SD package to deploy BIOS updates should work, but not tried yet.
Dell 64BIT BIOS Flash Utility | Dell US
If you are a Dell shop another option is Dell's Command Update utility. The utility itself is fairly easy to deploy from SD package (DCU_Setup_2.3.1.exe /S /V"/l*v \"$rf\" /QB-! REBOOT=ReallySuppress "). After it's installed you can force machines to update Drivers and BIOS via CLI. Not tried it yet, but there is a Dell whitepaper on using DCU + Dell Repistory Manager to control updates.
Dell Command Update
http://en.community.dell.com/techcenter/enterprise-client/w/wiki/7534.dell-command-update
Dell Repository Manager
http://www.dell.com/support/home/us/en/19/Drivers/DriversDetails?driverid=2GY7P
Dell whitepaper on DCU & DRM.
http://en.community.dell.com/techcenter/extras/m/white_papers/19997711/download