I have the Sendero Seeing Eye app and no external receiver, and it works ok. The extra receiver may help in some situations and also with battery life. But you don't need it to use the app. Mary Mary Otten motten53@xxxxxxxxx To change your email settings (unsubscribe, digest only, or vacation mode): http://senderogroup.com/social_media/email.htm Additionally, to unsubscribe send an email to gps-talkusers-request@xxxxxxxxxxxxx with "unsubscribe" in the Subject.