Sakshi Ganapathy is a temple present in Srisailam. It's about 3 miles far from Mallikarjuna Temple in Srisailam. Going to Srisailam was very difficult in those days as it is in a mountain. Today, we have buses and cars but those days they didn't have this facility. Our Acharyal has also visited Srisailam.
Lord Shiva thought "People are coming to Srisailam with lots of difficulties. We should do something special to those who come here". But, he is also called Asutoshi(ஆசுதோஷி), the one who blesses people very easily, even though they do fake devotion. When the ocean was churned for nectar, the Devas took the nectar and other great things, leaving the Hala Hala poison for Lord Shiva. Lord Shiva lives in Kasi(Varnasi) and he established a rule that the people leaving their mortal body in Kasi would be blessed with Salvation. At the same time, he also blesses people visitiing Kumbakonam to attain salvation if they couldn't come to Kasi.
Lord Vinayaka thought "These kind of relaxations should not happen for Srisailam". He went to his father and told "Only the people coming to Srisailam should get the benefits applicable for Srisailam. You have an attitude of mercy. Others can easily cheat you by saying that he/she has gone to the place. To prevent these things, I will be present as Sakshi Ganapathy, noting the name, place and the date of arrival of the visiting person". Lord Shiva also agreed.
At the border of Srisailam, Lord Vinayaka is present with the name 'Sakshi Ganapathy'. Today, he is present in the form of an idol. Difference with other Ganapathy idols is in the lower two hands where he holds a book and a pen. He records the name, place of the person and date of his/her arrival. At last, before completing the Srisailam Yatra, one should go to this temple and ask his permission to leave. Generally, we worship Lord Vinayaka at the beginning, but in this place we worship him at the end. If we come to the temple, Lord Vinayaka starts writing our details and reports to his father "They came! I am the witness" and delivers the Prasada of Lord Shiva.
In order to be fair to the people who have visited Srisailam with great difficulty, Lord Vinayaka himself sat there with a book, pen and a name(Sakshi Ganapathy) to note down the statistics as shown in the below picture. Let us all prostrate before Lord Vinayaka who is so much merciful.