I'm posting another answer because I've learned a new method for checking the status of the Editor in ArcMap using ArcObjects and Python together. My answer borrows heavily from the work done by Mark Cederholm as referenced in this post: How do I access ArcObjects from Python?, and code examples provided by Matt Wilkie in his "Snippits.py" file. You will need to follow the instructions provided in the first answer to download and install comtypes and then get a copy of the Snippets.py script. I am posting a copy of the essential functions from that script below.

When the function ArcMap_GetEditSessionStatus() is called, it will check the current state of the Editor in ArcMap and return true or false. This lets me check if a user is prepared to use my tool or if they need to be prompted to start an edit session. The downside to this method is the requirement to install comtypes before ArcObjects can be used in Python, so sharing a tool that requires this package in a multi-user office environment might not be possible. With my limited experience I'm not sure how to bundle it all together for easy sharing as an Esri Python tool add-in. Suggestions for how to do this would be appreciated.

#From the Snippits.py file created by Matt Wilkie
def NewObj(MyClass, MyInterface):
    """Creates a new comtypes POINTER object where\n\
    MyClass is the class to be instantiated,\n\
    MyInterface is the interface to be assigned"""
    from comtypes.client import CreateObject
    try:
        ptr = CreateObject(MyClass, interface=MyInterface)
        return ptr
    except:
        return None

def CType(obj, interface):
    """Casts obj to interface and returns comtypes POINTER or None"""
    try:
        newobj = obj.QueryInterface(interface)
        return newobj
    except:
        return None

def CLSID(MyClass):
    """Return CLSID of MyClass as string"""
    return str(MyClass._reg_clsid_)

def GetApp(app="ArcMap"):
    """app must be 'ArcMap' (default) or 'ArcCatalog'\n\
    Execute GetDesktopModules() first"""
    if not (app == "ArcMap" or app == "ArcCatalog"):
        print "app must be 'ArcMap' or 'ArcCatalog'"
        return None
    import comtypes.gen.esriFramework as esriFramework
    import comtypes.gen.esriArcMapUI as esriArcMapUI
    import comtypes.gen.esriCatalogUI as esriCatalogUI
    pAppROT = NewObj(esriFramework.AppROT, esriFramework.IAppROT)
    iCount = pAppROT.Count
    if iCount == 0:
        return None
    for i in range(iCount):
        pApp = pAppROT.Item(i)
        if app == "ArcCatalog":
            if CType(pApp, esriCatalogUI.IGxApplication):
                return pApp
            continue
        if CType(pApp, esriArcMapUI.IMxApplication):
            return pApp
    return None


def GetModule(sModuleName):
    """Import ArcGIS module"""
    from comtypes.client import GetModule
    sLibPath = GetLibPath()
    GetModule(sLibPath + sModuleName)


def GetDesktopModules():
    """Import basic ArcGIS Desktop libraries"""
    GetModule("esriFramework.olb")
    GetModule("esriArcMapUI.olb")

#My added function for checking edit session status
def ArcMap_GetEditSessionStatus():

    GetDesktopModules()
    GetModule("esriEditor.olb")
    import comtypes.gen.esriSystem as esriSystem
    import comtypes.gen.esriEditor as esriEditor
    pApp = GetApp()
    pID = NewObj(esriSystem.UID, esriSystem.IUID)
    pID.Value = CLSID(esriEditor.Editor)
    pExt = pApp.FindExtensionByCLSID(pID)
    pEditor = CType(pExt, esriEditor.IEditor)
    if pEditor.EditState == esriEditor.esriStateEditing:
        print "Edit session active"
        return True
    else:
        print "Not in an edit session"
        return False