I suppose you are looking for a customer facing application. There are several options available today and the best way to check is through our published site https://docs.oracle.com/cd/E98457_01/docs/Certified%20Third-Party%20Interfaces%20-%20OPERA%205.pdf.
For OPERA there are few I can recommend to you such as Samsotech, StayNTouch, Zaplox, Ariane, and Hotelbird which are common in Europe and Asia.
Good morning Ayman,
though not a 100% check in state, I want to make you aware of the fact that since Suite8 version 188.8.131.52 customers who have both Suite8 and WebConnect (must be then updated to the above-mentioned version) can enjoy a new interesting feature such as PRE Check In. This is done online of course. Guests can pre check-in PRIOR to the arrival date, as well as have the possibility to choose their own room. In fact rooms management in Suite8 for Pre-Check in works similarly to Rooms Management for kiosk check in.
Otherwise for best-in-class customer journey experience and 100% customer-facing mobile applications, I advise your customer/s opt for one of the available Interfaces with one of the previously mentioned vendors.