I have been using a RFM2Pi (aka RFM12Pi) with a hardwired serial connection to a Raspberry Pi for the last 4 years with no problems. My RFM12Pi has a RFM69 rather than RFM12. This is how I have been getting data from various EmonTH sensors with RFM69 transmitters to Emoncms.
Recently I decided to try a WiFi connection to the Pi instead of hardwired. After trying a few RFM69 to WiFi gateways, I decided to use a “esp-link” running on a Wemos D1 Mini with the existing RFM2Pi hardware/software. This solution is from the great people at JeeLabs ( GitHub - jeelabs/esp-link: esp8266 wifi-serial bridge, outbound TCP, and arduino/AVR/LPC/NXP programmer ). It turned out to work very well, and the web interface built-in to the esp-link software has a feature to view incoming data. No modifications were necessary to my RFM2Pi. I would highly recommend this solution.