There is an SNMP MIB RFC, that is targeting this topic: http://tools.ietf.org/html/rfc3805
But, as the others mentioned, there is no actually universal method to get such information, since SNMP manageability is far from being common, even at the high-end models. Those "low cost" printers and their drivers that can actually alert the user, are using proprietary methods to do that. But these interfaces are not public. Even if the driver is capable of displaying ink status, an external application most likely won't be able to do the same.
Manufacturers targeting enterprises (like HP), are also not always using SNMP, but they might give you tools to manage your printer assets - if you use their printers.