Dunno if this has gotten answered, but had to deal with this today and the app Groupy is great. you can even hide groups so it lists only the ones you want, it handles multiple accounts setup on the phone just fine, and I know for sure if you drop a shortcut to the app itself it will open right up once you tap the 1x1 shortcut on the desktop right to the listing of the groups.
It also has some nice shortcut buttons to send an Email, SMS [or MMS] right from that listing screen [the icons are right across the bottom of the screen when the app is open.
I didn't see any widgets listed under widgets for it, but I haven't gone extremely in-depth with it yet. I don't see a major need for them as when you tap the app shortcut the app opens right to a list of all the groups you have on the device [be they system, or created by you the user (if done via google contacts website be sure to either wait for the sync or go in to settings accounts and tap the account you modified contacts on and tap to clear then tap to add the checkmark back as that will cause it to sync right away [or of course hit sync now button if you have that available instead if you prefer]).
Of course if you go through and choose to hide any groups when you open the app it will only list that groups that have not been hidden.
You can even choose multiple groups to send messages to by tapping the checkboxes found on the right hand side of the screen for all the groups you want to send your message to.
PLEASE BE AWARE FOR BOTH EMAIL AND SMS OR MMS: Some carriers/providers do put limits on how many contacts you may send any one message to in attempts to curtail people from spamming too many people at once. You will need to review the limits with your carrier in the case of SMS/MMS messages OR you provider for your email account for emails.
So if your groups [or groups] contain too many people your message may either fail to send at all or only send to soo many people [depending on how your carrier/service provider choose to handle the limit]